Techniques for configuring preamble and overhead signals for transmissions in an unlicensed radio frequency spectrum band

ABSTRACT

Techniques are described for wireless communication. A first method includes transmitting a first signal to indicate accessing a first channel in a radio frequency spectrum band, and transmitting information with the first signal in the radio frequency spectrum band. A second method includes winning contention to access a radio frequency spectrum band, and after the winning contention to access the radio frequency spectrum band, transmitting a first signal to align a starting point of a second signal with a reference boundary associated with the radio frequency spectrum band. A third method includes winning contention to access a radio frequency spectrum band during a first frame period, the first frame selected from a plurality of different frame periods, and transmitting a signal at a periodicity during one or more subframes of the first frame period for each of the plurality of different frame periods.

CROSS REFERENCES

The present application for patent claims priority to U.S. ProvisionalPatent Application No. 61/969,080 by Luo et al., entitled “Techniquesfor Configuring Preamble and Overhead Signals for Transmissions in anUnlicensed Radio Frequency Spectrum Band,” filed Mar. 21, 2014, and U.S.Provisional Patent Application No. 61/992,174 by Luo et al., entitled“Techniques for Configuring Preamble and Overhead Signals forTransmissions in an Unlicensed Radio Frequency Spectrum Band,” filed May12, 2014, assigned to the assignee hereof, and which are herebyincorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure, for example, relates to wireless communicationsystems, and more particularly to techniques for configuring preambleand overhead signals for transmissions in a radio frequency spectrumband.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing the available system resources (e.g., time, frequency, andpower). Examples of such multiple-access systems include code-divisionmultiple access (CDMA) systems, time-division multiple access (TDMA)systems, frequency-division multiple access (FDMA) systems, andorthogonal frequency-division multiple access (OFDMA) systems.

By way of example, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple UEs. A base station may communicate with UEson downlink channels (e.g., for transmissions from a base station to aUE) and uplink channels (e.g., for transmissions from a UE to a basestation).

Some modes of communication may enable communications with a UE overdifferent radio frequency spectrum bands (e.g., a licensed radiofrequency spectrum band and/or an unlicensed radio frequency spectrumband) of a cellular network. With increasing data traffic in cellularnetworks, the offloading of at least some data traffic to an unlicensedradio frequency spectrum band may provide a cellular operator withopportunities for enhanced data transmission capacity. Also, a pluralityof mobile network operators may compete with each other to access ashared licensed radio frequency spectrum which the operators areauthorized to access. Prior to gaining access to and transmitting dataover the licensed radio frequency spectrum band, a transmittingapparatus may, in some examples, perform a listen before talk (LBT)procedure to gain access to the radio frequency spectrum band. An LBTprocedure may include performing a clear channel assessment (CCA) todetermine whether a channel of the radio frequency spectrum band isavailable. When it is determined that the channel of the radio frequencyspectrum band is not available (e.g., because another device is alreadyusing the channel of the radio frequency spectrum band), a CCA may beperformed for the channel again at a later time.

In some cases, transmissions by one or more nodes over a radio frequencyspectrum band (e.g., Wi-Fi nodes and/or nodes of other operators) mayprevent a base station or UE from gaining access to the radio frequencyspectrum, resulting in the base station or UE being “starved” of use ofthe radio frequency spectrum band. In some cases, this starvationproblem may be mitigated by using an LBT protocol configured for loadbased equipment (LBT-LBE) instead of an LBT protocol configured forframe based equipment (LBT-FBE). In an LBT-LBE protocol, an extended CCAprocedure including a plurality of N CCA procedures may be performed.The extended CCA procedure performed in conjunction with an LBT-LBEprotocol may provide a base station or UE a better chance to gain accessto a radio frequency spectrum band (e.g., compared to a single CCAprocedure performed in conjunction with an LBT-FBE protocol).

SUMMARY

The present disclosure, for example, relates to one or more techniquesfor configuring preamble and overhead signals for transmissions in aradio frequency spectrum band. In some examples, the techniques mayinclude transmitting information in a preamble signal in a radiofrequency spectrum band. The transmitted information may aid a receivingapparatus in decoding a transmission that follows the information and/orenable the receiving apparatus to conserve power, etc. In some examples,the techniques may include transmitting a first signal to align astarting point of a second signal with a reference boundary associatedwith a radio frequency spectrum band. The first signal may betransmitted after winning contention to access the radio frequencyspectrum band. The first signal may be used, for example, to reserve thechannel and/or transmit information over the channel. In some examples,the techniques may include transmitting a signal to convert a locationof overhead signals in relation to the timing of a radio frame boundary.In some examples, the techniques may include configuring one or moreoverhead channel transmissions at a periodicity, at a time or timesand/or at a frequency location and/or locations, regardless of theduration (e.g., two milliseconds, five milliseconds, and/or tenmilliseconds) of an LBT radio frame period in which an LBT procedureoccurs. This may, in some examples, reduce the processing burdenassociated with the overhead transmissions.

In a first set of illustrative examples, a method for wirelesscommunication is described. In one example, the method may includetransmitting a first signal to indicate accessing a first channel in aradio frequency spectrum band, and transmitting information with thefirst signal in the radio frequency spectrum band.

In some examples of the method, the information may include systeminformation. In some examples, the information may indicate a framestructure for transmission in the radio frequency spectrum band. In someexamples, the information may indicate an uplink configuration or adownlink configuration for transmission in the radio frequency spectrumband. In some examples, the information may indicate a number ofsubframes of a frame that are used for transmission in the radiofrequency spectrum band.

In some examples of the method, the transmitting information with thefirst signal may include transmitting information as part of the firstsignal. The first signal may, in some examples, be generated based atleast in part on a sequence. The sequence may, in some examples, be afunction of the information. In some examples, the information mayinclude a cell identifier (ID), a public land mobile network ID, or acombination thereof.

In some examples of the method, the transmitting information with thefirst signal may include transmitting information in a second signalalong with the first signal. The second signal may be separate from thefirst signal.

In some examples, the method may include selecting a first phase fromamong a plurality of phases for transmission of the first signal.Different phases of the plurality of phases may correspond to differentinformation. In these examples, the transmitting information with thefirst signal may include transmitting the first signal at the firstphase.

In some examples, the first signal and the information may betransmitted during a single orthogonal frequency-division multiplexing(OFDM) symbol period of the radio frequency spectrum band.

In some examples, the first signal may be transmitted during a firstOFDM symbol period of the radio frequency spectrum band and a secondOFDM symbol period of the radio frequency spectrum band, and theinformation may be transmitted during the second OFDM symbol period. Inthese examples, the method may include transmitting a second signalcarrying the information during the second OFDM symbol period of theradio frequency spectrum band. In these latter examples, the firstsignal may provide a phase reference for the second signal.

In some examples, the information may indicate a number of antennas touse for receiving a transmission carried on a component carrier in theradio frequency spectrum band. In these examples, the method may includeadjusting a modulation and coding scheme (MCS) for transmission of thecomponent carrier in the radio frequency spectrum band based at least inpart on the number of antennas to use to receive the component carrierin the radio frequency spectrum band. In some examples, the number ofantennas to use for receiving a transmission carried on the componentcarrier in the radio frequency spectrum band may be determined based atleast in part on an uplink configuration or a downlink configurationassociated with the component carrier. In some examples, the number ofantennas to use for receiving a transmission carried on the componentcarrier in the radio frequency spectrum band may be determined based atleast in part on a clear channel assessment (CCA) procedure associatedwith each of a plurality of component carriers used to serve a userequipment (UE). In some examples, the method may include selecting thenumber of antennas to use for receiving a transmission carried on thecomponent carrier in the radio frequency spectrum band for each subframeof a frame of the component carrier in the radio frequency spectrumband.

In a second set of illustrative examples, an apparatus for wirelesscommunication is described. In one example, the apparatus may includemeans for transmitting a first signal to indicate accessing a firstchannel in a radio frequency spectrum band, and means for transmittinginformation with the first signal in the radio frequency spectrum band.In some examples, the apparatus may further include means forimplementing one or more aspects of the method for wirelesscommunication described above with respect to the first set ofillustrative examples.

In a third set of illustrative examples, another apparatus for wirelesscommunication is described. In one example, the apparatus may include aprocessor, memory in electronic communication with the processor, andinstructions stored in the memory. The instructions may be executable bythe processor to transmit a first signal to indicate accessing a firstchannel in a radio frequency spectrum band, and to transmit informationwith the first signal in the radio frequency spectrum band. In someexamples, the instructions may also be executable by the processor toimplement one or more aspects of the method for wireless communicationdescribed above with respect to the first set of illustrative examples.

In a fourth set of illustrative examples, a computer program product forcommunication by a wireless communication apparatus in a wirelesscommunication system is described. In one example, the computer programproduct may include a non-transitory computer-readable medium storinginstructions executable by a processor to cause the wirelesscommunication apparatus to transmit a first signal to indicate accessinga first channel in a radio frequency spectrum band, and to transmitinformation with the first signal in the radio frequency spectrum band.In some examples, the instructions may also be executable by theprocessor to cause the wireless communication apparatus to implement oneor more aspects of the method for wireless communication described abovewith respect to the first set of illustrative examples.

In a fifth set of illustrative examples, a method for wirelesscommunication is described. In one example, the method may includewinning contention to access a radio frequency spectrum band. The methodmay also include, after the winning contention to access the radiofrequency spectrum band, transmitting a first signal to align a startingpoint of a second signal with a reference boundary associated with theradio frequency spectrum band.

In some examples, the method may include accessing timing information,and determining the reference boundary based at least in part on thetiming information and the winning contention to access the radiofrequency spectrum band.

In some examples of the method, the first signal may include a variablelength training sequence. In some examples, the first signal may includea variable length training sequence and at least one fixed lengthtraining sequence.

In some examples, the method may include transmitting information aspart of the first signal.

In some examples, the first signal may be usable for automatic gaincontrol (AGC) by a user equipment (UE).

In some examples, the method may include operating in an LBT-LBE mode ofoperation in the radio frequency spectrum band. In some examples of themethod, the reference boundary may include a boundary of an OFDM symbolperiod. In these examples, the first signal may be associated with acontention priority, and the first signal may be transmitted during aportion of the OFDM symbol period based at least in part on thecontention priority. In some examples of the method, the referenceboundary may include a boundary of a slot of a frame associated with theradio frequency spectrum band. In some examples of the method, thereference boundary may include a boundary of a subframe of a frameassociated with the radio frequency spectrum band.

In some examples of the method, the second signal may include a signalindicating the winning contention to access the radio frequency spectrumband. In some examples, the first signal may be transmitted before thesecond signal.

In a sixth set of illustrative examples, an apparatus for wirelesscommunication is described. In one example, the apparatus may includemeans for winning contention to access a radio frequency spectrum band.The apparatus may also include means for, after the winning contentionto access the radio frequency spectrum band, transmitting a first signalto align a starting point of a second signal with a reference boundaryassociated with the radio frequency spectrum band. In some examples, theapparatus may further include means for implementing one or more aspectsof the method for wireless communication described above with respect tothe fifth set of illustrative examples.

In a seventh set of illustrative examples, another apparatus forwireless communication is described. In one example, the apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to win contention to access a radiofrequency spectrum band. The instructions may also be executable by theprocessor to, after winning contention to access the radio frequencyspectrum band, transmit a first signal to align a starting point of asecond signal with a reference boundary associated with the radiofrequency spectrum band. In some examples, the instructions may also beexecutable by the processor to implement one or more aspects of themethod for wireless communication described above with respect to thefifth set of illustrative examples.

In an eighth set of illustrative examples, a computer program productfor communication by a wireless communication apparatus in a wirelesscommunication system is described. In one example, the computer programproduct may include a non-transitory computer-readable medium storinginstructions executable by a processor to cause the wirelesscommunication apparatus to win contention to access a radio frequencyspectrum band. The instructions may also be executable by the processorto cause the wireless communication apparatus to, after winningcontention to access the radio frequency spectrum band, transmit a firstsignal to align a starting point of a second signal with a referenceboundary associated with the radio frequency spectrum band. In someexamples, the instructions may also be executable by the processor tocause the wireless communication apparatus to implement one or moreaspects of the method for wireless communication described above withrespect to the fifth set of illustrative examples.

In a ninth set of illustrative examples, a method for wirelesscommunication is described. In one example, the method may includewinning contention to access a radio frequency spectrum band during afirst frame period. The first frame may be selected from a plurality ofdifferent frame periods. The method may also include transmitting asignal at a periodicity during one or more subframes of the first frameperiod for each of the plurality of different frame periods.

In some examples of the method, the periodicity may be a fixedperiodicity.

In some examples of the method, the transmitting the signal at theperiodicity may include transmitting the signal at a fixed time and afixed frequency location.

In some examples of the method, the signal may be transmitted in anoverhead channel.

In some examples of the method, the first frame period may include alisten before talk (LBT) frame period.

In some examples, the method may include determining whether the signalcollides with a timing of a contention procedure, and preventingtransmission of the signal based at least in part on the determinationthat the signal collides with the timing of the contention procedure.

In a tenth set of illustrative examples, an apparatus for wirelesscommunication is described. In one example, the apparatus may includemeans for winning contention to access a radio frequency spectrum bandduring a first frame period. The first frame may be selected from aplurality of different frame periods. The apparatus may also includemeans for transmitting a signal at a periodicity during one or moresubframes of the first frame period for each of the plurality ofdifferent frame periods. In some examples, the apparatus may furtherinclude means for implementing one or more aspects of the method forwireless communication described above with respect to the ninth set ofillustrative examples.

In an eleventh set of illustrative examples, another apparatus forwireless communication is described. In one example, the apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to win contention to access a radiofrequency spectrum band during a first frame period. The first frame maybe selected from a plurality of different frame periods. Theinstructions may also be executable by the processor to transmit asignal at a periodicity during one or more subframes of the first frameperiod for each of the plurality of different frame periods. In someexamples, the instructions may also be executable by the processor toimplement one or more aspects of the method for wireless communicationdescribed above with respect to the ninth set of illustrative examples.

In a twelfth set of illustrative examples, a computer program productfor communication by a wireless communication apparatus in a wirelesscommunication system is described. In one example, the computer programproduct may include a non-transitory computer-readable medium storinginstructions executable by a processor to cause the wirelesscommunication apparatus to win contention to access a radio frequencyspectrum band during a first frame period. The first frame may beselected from a plurality of different frame periods. The instructionsmay also be executable by the processor to cause the wirelesscommunication apparatus to transmit a signal at a periodicity during oneor more subframes of the first frame period for each of the plurality ofdifferent frame periods. In some examples, the instructions may also beexecutable by the processor to cause the wireless communicationapparatus to implement one or more aspects of the method for wirelesscommunication described above with respect to the ninth set ofillustrative examples.

In a thirteenth set of illustrative examples, another method forwireless communication is described. In one example, the method mayinclude winning contention to access a radio frequency spectrum band;after the winning contention to access the radio frequency spectrumband, transmitting a first signal to indicate a timing of a radio frameboundary associated with the radio frequency spectrum band; andtransmitting a second signal to convey location information for overheadsignals in relation to the timing of the radio frame boundary.

In some examples of the method, the second signal may include radioresource control (RRC) signaling. In some examples of the method, thesecond signal may convey location information for a downlink controlchannel in relation to the radio frame boundary. In some examples, thesecond signal may convey location information for resources used forchannel state information (CSI) feedback.

In some examples, the method may include operating in alisten-before-talk (LBT) load based equipment (LBE) mode of operationover the radio frequency spectrum band. In some examples, the firstsignal may include the second signal.

In a fourteenth set of illustrative examples, an apparatus for wirelesscommunication is described. In one example, the apparatus may includemeans for winning contention to access a radio frequency spectrum band;means for transmitting, after the winning contention to access the radiofrequency spectrum band, a first signal to indicate a timing of a radioframe boundary associated with the radio frequency spectrum band; andmeans for transmitting a second signal to convey location informationfor overhead signals in relation to the timing of the radio frameboundary. In some examples, the apparatus may further include means forimplementing one or more aspects of the method for wirelesscommunication described above with respect to the thirteenth set ofillustrative examples.

In a fifteenth set of illustrative examples, another apparatus forwireless communication is described. In one example, the apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to win contention to access a radiofrequency spectrum band; to transmit, after the winning contention toaccess the radio frequency spectrum band, a first signal to indicate atiming of a radio frame boundary associated with the radio frequencyspectrum band; and to transmit a second signal to convey locationinformation for overhead signals in relation to the timing of the radioframe boundary. In some examples, the instructions may also beexecutable by the processor to implement one or more aspects of themethod for wireless communication described above with respect to thethirteenth set of illustrative examples.

In a sixteenth set of illustrative examples, a computer program productfor communication by a wireless communication apparatus in a wirelesscommunication system is described. In one example, the computer programproduct may include a non-transitory computer-readable medium storinginstructions executable by a processor to cause the wirelesscommunication apparatus to win contention to access a radio frequencyspectrum band; to transmit, after the winning contention to access theradio frequency spectrum band, a first signal to indicate a timing of aradio frame boundary associated with the radio frequency spectrum band;and to transmit a second signal to convey location information foroverhead signals in relation to the timing of the radio frame boundary.In some examples, the instructions may also be executable by theprocessor to cause the wireless communication apparatus to implement oneor more aspects of the method for wireless communication described abovewith respect to the thirteenth set of illustrative examples.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the spirit and scope of the appended claims. Features whichare believed to be characteristic of the concepts disclosed herein, bothas to their organization and method of operation, together withassociated advantages will be better understood from the followingdescription when considered in connection with the accompanying figures.Each of the figures is provided for the purpose of illustration anddescription only, and not as a definition of the limits of the claims.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a block diagram of a wireless communication system, inaccordance with various aspects of the present disclosure;

FIG. 2 shows a wireless communication system in which LTE/LTE-A isdeployed under different scenarios using an unlicensed radio frequencyspectrum band, in accordance with various aspects of the presentdisclosure;

FIG. 3 shows examples of a gating interval (or LBT radio frame) for acellular downlink in an unlicensed radio frequency spectrum band, inaccordance with various aspects of the present disclosure;

FIG. 4 shows an example of a wireless communication over an unlicensedradio frequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 5 shows an example of a wireless communication over an unlicensedradio frequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 6 shows an example of resource allocations for CCA-ExemptTransmissions (CETs) of synchronous operators in an unlicensed radiofrequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 7 shows a timing diagram of wireless communications over anunlicensed radio frequency spectrum band, in accordance with variousaspects of the present disclosure;

FIG. 8A shows an example of how information may be transmitted with afirst signal (e.g., a channel usage beacon signal (CUBS)) that indicatesaccessing a channel in a radio frequency spectrum band, in accordancewith various aspects of the present disclosure;

FIG. 8B shows an example of how information may be transmitted with afirst signal (e.g., a CUBS) that indicates accessing a channel in aradio frequency spectrum band, in accordance with various aspects of thepresent disclosure;

FIG. 9 shows an example of how information indicating a number ofantennas to use for receiving a transmission carried on a componentcarrier may be determined and used, in accordance with various aspectsof the present disclosure;

FIG. 10 shows an example of how information indicating a number ofantennas to use for receiving a transmission carried on a componentcarrier may be determined and used, in accordance with various aspectsof the present disclosure;

FIG. 11A shows an example of how a first signal may be transmitted toalign a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure;

FIG. 11B shows an example of how a first signal may be transmitted toalign a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure;

FIG. 11C shows an example of how a first signal may be transmitted toalign a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure;

FIG. 12 shows an example of how a first signal may be transmitted whileoperating in an LBT-LBE mode of operation in a radio frequency spectrumband, to align a starting point of a second signal with a referenceboundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure;

FIG. 13 shows an example of how a first signal may be transmitted whileoperating in an LBT-LBE mode of operation in a radio frequency spectrumband, to align a starting point of a second signal with a referenceboundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure;

FIG. 14 shows an example of how a first signal may be transmitted whileoperating in an LBT-LBE mode of operation in a radio frequency spectrumband, to align a starting point of a second signal with a referenceboundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure;

FIG. 15 shows an example of how a first signal may be transmitted whileoperating in an LBT-LBE mode of operation in a radio frequency spectrumband, to align a starting point of a second signal with a referenceboundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure;

FIG. 16 shows an example of how one or more overhead transmission may bemade in a radio frequency spectrum band, in accordance with variousaspects of the present disclosure;

FIG. 17 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 18 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 19 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 20 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 21 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 22 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 23 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 24 shows a block diagram of an apparatus for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 25 shows a block diagram of a base station (e.g., a base stationforming part or all of an eNB) for use in wireless communication, inaccordance with various aspects of the present disclosure;

FIG. 26 shows a block diagram of a UE for use in wireless communication,in accordance with various aspects of the present disclosure;

FIG. 27 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 28 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 29 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 30 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 31 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 32 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure;

FIG. 33 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure; and

FIG. 34 is a flow chart illustrating an example of a method for wirelesscommunication, in accordance with various aspects of the presentdisclosure.

DETAILED DESCRIPTION

Techniques are described in which preamble and/or overhead signals areconfigured for transmissions in a radio frequency spectrum band (e.g.,an unlicensed radio frequency spectrum band for which apparatuses mayneed to contend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use, or a shared licensedradio frequency band which a plurality of mobile network operators areauthorized to access). In some examples, the radio frequency spectrumband may be used for cellular communications (e.g., Long Term Evolution(LTE) communications and/or LTE-Advanced (LTE-A) communications).

With increasing data traffic in cellular networks, the offloading of atleast some data traffic to a radio frequency spectrum band may provide acellular operator (e.g., an operator of a public land mobile network(PLMN) and/or a coordinated set of base stations defining a cellularnetwork, such as an LTE/LTE-A network) with opportunities for enhanceddata transmission capacity. Prior to gaining access to, andcommunicating data over, the radio frequency spectrum band, atransmitting apparatus may, in some examples, perform an LBT procedureto gain access to the radio frequency spectrum band. Such an LBTprocedure may include performing a CCA to determine whether a channel ofthe radio frequency spectrum band is available. When it is determinedthat a channel is not available, a CCA may be performed for the channelagain at a later time.

In some examples of the described techniques, information (e.g., N bitsof information) may be transmitted over a channel in a radio frequencyspectrum band by transmitting the information with a signal thatindicates accessing (e.g., the reserving of) the channel in the radiofrequency spectrum band. In an example, the information may betransmitted as part of the signal that indicates accessing the channelin the radio frequency spectrum band. In another example, theinformation may be transmitted as a separate signal along with thesignal that indicates accessing the channel in the radio frequencyspectrum band. The transmitted information may aid a receiving apparatusin decoding a transmission that follows the information and/or enablethe receiving apparatus to conserve power, etc.

In some examples of the described techniques, a first signal may betransmitted when a successful contention procedure (e.g., an LBTprocedure) concludes before a reference boundary associated with a radiofrequency spectrum band (e.g., before a boundary of a next orthogonalfrequency-division multiplexing (OFDM) symbol period associated with theradio frequency spectrum band, a boundary of a slot of a frameassociated with the radio frequency spectrum band, and/or a boundary ofa subframe of a frame associated with the radio frequency spectrumband). The first signal may be used to align a starting point of asecond signal with the reference boundary associated with the radiofrequency spectrum band. In some examples, the commencement of the firstsignal may not coincide with a reference boundary of the radio frequencyspectrum band, and the length of the first signal may be variable due tovariances in the timing between when a contention procedure is performedand when a reference boundary (e.g., a boundary of a next OFDM symbolperiod) occurs.

In some examples of the described techniques, one or more overheadchannel transmissions (e.g., eCRS and/or CSI-RS transmissions) may betransmitted with a periodicity, at a time or times and/or at a frequencylocation and/or locations, regardless of the duration (e.g., twomilliseconds, five milliseconds, and/or ten milliseconds) of an LBTradio frame period. For example, one or more overhead channeltransmissions may be made during one or more subframes regardless of theduration of an LBT radio frame in which the subframes occur.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (WiFi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM™, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description below, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the spirit and scope of the disclosure. Various examplesmay omit, substitute, or add various procedures or components asappropriate. For instance, the methods described may be performed in anorder different from that described, and various steps may be added,omitted, or combined. Also, features described with respect to someexamples may be combined in other examples.

FIG. 1 shows a block diagram of a wireless communication system 100, inaccordance with various aspects of the present disclosure. The wirelesscommunication system 100 may include a plurality of base stations 105(e.g., base stations forming parts or all of one or more eNBs), a numberof UEs 115, and a core network 130. Some of the base stations 105 maycommunicate with the UEs 115 under the control of a base stationcontroller (not shown), which may be part of the core network 130 orcertain ones of the base stations 105 in various examples. Some of thebase stations 105 may communicate control information and/or user datawith the core network 130 through backhaul 132. In some examples, someof the base stations 105 may communicate, either directly or indirectly,with each other over backhaul links 134, which may be wired or wirelesscommunication links. The wireless communication system 100 may supportoperation on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters can transmit modulated signalssimultaneously on the multiple carriers. For example, each communicationlink 125 may be a multi-carrier signal modulated according to variousradio technologies. Each modulated signal may be sent on a differentcarrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, data, etc.

The base stations 105 may wirelessly communicate with the UEs 115 viaone or more base station antennas. Each of the base stations 105 mayprovide communication coverage for a respective coverage area 110. Insome examples, a base station 105 may be referred to as an access point,a base transceiver station (BTS), a radio base station, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, an evolved NodeB (eNB), a Home NodeB, a Home eNodeB, a WLANaccess point, a Wi-Fi node or some other suitable terminology. Thecoverage area 110 for a base station 105 may be divided into sectorsmaking up only a portion of the coverage area. The wirelesscommunication system 100 may include base stations 105 of differenttypes (e.g., macro, micro, and/or pico base stations). The base stations105 may also utilize different radio technologies, such as cellularand/or WLAN radio access technologies. The base stations 105 may beassociated with the same or different access networks or operatordeployments. The coverage areas of different base stations 105,including the coverage areas of the same or different types of basestations 105, utilizing the same or different radio technologies, and/orbelonging to the same or different access networks, may overlap.

In some examples, the wireless communication system 100 may include anLTE/LTE-A communication system (or network), which LTE/LTE-Acommunication system may support one or more modes of operation ordeployment in a licensed radio frequency spectrum band (e.g., a radiofrequency spectrum band for which apparatuses may not contend for accessbecause the spectrum band is licensed to particular users for particularuses) and/or an unlicensed radio frequency spectrum band (e.g., a radiofrequency spectrum band for which apparatuses may need to contend foraccess because the radio frequency spectrum band is available forunlicensed use, such as Wi-Fi use). In other examples, the wirelesscommunication system 100 may support wireless communication using one ormore access technologies different from LTE/LTE-A. In LTE/LTE-Acommunication systems, the term evolved NodeB or eNB may be, forexample, used to describe ones or groups of the base stations 105.

The wireless communication system 100 may be or include a HeterogeneousLTE/LTE-A network in which different types of base stations 105 providecoverage for various geographical regions. For example, each basestation 105 may provide communication coverage for a macro cell, a picocell, a femto cell, and/or other type of cell. Small cells such as picocells, femto cells, and/or other types of cells may include low powernodes or LPNs. A macro cell, for example, covers a relatively largegeographic area (e.g., several kilometers in radius) and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A pico cell would, for example, cover a relatively smallergeographic area and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A femto cell would also, forexample, cover a relatively small geographic area (e.g., a home) and, inaddition to unrestricted access, may also provide restricted access byUEs having an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a picocell may be referred to as a pico eNB. And, an eNB for a femto cell maybe referred to as a femto eNB or a home eNB. An eNB may support one ormultiple (e.g., two, three, four, and the like) cells.

The core network 130 may communicate with the base stations 105 via abackhaul 132 (e.g., S1 application protocol, etc.). The base stations105 may also communicate with one another, e.g., directly or indirectlyvia backhaul links 134 (e.g., X2 application protocol, etc.) and/or viabackhaul 132 (e.g., through core network 130). The wirelesscommunication system 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frameand/or gating timing, and transmissions from different eNBs may beapproximately aligned in time. For asynchronous operation, the eNBs mayhave different frame and/or gating timing, and transmissions fromdifferent eNBs may not be aligned in time.

The UEs 115 may be dispersed throughout the wireless communicationsystem 100. A UE 115 may also be referred to by those skilled in the artas a mobile device, a mobile station, a subscriber station, a mobileunit, a subscriber unit, a wireless unit, a remote unit, a wirelessdevice, a wireless communication device, a remote device, a mobilesubscriber station, an access terminal, a mobile terminal, a wirelessterminal, a remote terminal, a handset, a user agent, a mobile client, aclient, or some other suitable terminology. A UE 115 may be a cellularphone, a personal digital assistant (PDA), a wireless modem, a wirelesscommunication device, a handheld device, a tablet computer, a laptopcomputer, a cordless phone, a wearable item such as a watch or glasses,a wireless local loop (WLL) station, etc. A UE 115 may be able tocommunicate with macro eNBs, pico eNBs, femto eNBs, relays, and thelike. A UE 115 may also be able to communicate over different types ofaccess networks, such as cellular or other WWAN access networks, or WLANaccess networks. In some modes of communication with a UE 115,communication may be conducted over a plurality of communication links125 or channels (i.e., component carriers), with each channel using acomponent carrier between the UE 115 and one of a number of cells (e.g.,serving cells, which cells may in some cases be operated by the same ordifferent base stations 105).

Each component carrier may be provided over a licensed radio frequencyspectrum band or an unlicensed radio frequency spectrum band, and a setof component carriers used in a particular mode of communication may allbe received (e.g., at a UE 115) over a licensed radio frequency spectrumband, all be received (e.g., at a UE 115) over an unlicensed radiofrequency spectrum band, or be received (e.g., at a UE 115) over acombination of a licensed radio frequency spectrum band and anunlicensed radio frequency spectrum band.

The communication links 125 shown in wireless communication system 100may include uplink channels (using component carriers) for carryinguplink (UL) communications (e.g., transmissions from a UE 115 to a basestation 105) and/or downlink channels (using component carriers) forcarrying downlink (DL) communications (e.g., transmissions from a basestation 105 to a UE 115). The UL communications or transmissions mayalso be called reverse link communications or transmissions, while theDL communications or transmissions may also be called forward linkcommunications or transmissions. The downlink communications and/oruplink communications may be made using a licensed radio frequencyspectrum band, an unlicensed radio frequency spectrum band, or both.

In some examples of the wireless communication system 100, LTE/LTE-A maybe deployed under different scenarios using an unlicensed radiofrequency spectrum band. The deployment scenarios may include asupplemental downlink mode in which LTE/LTE-A downlink communications ina licensed radio frequency spectrum band may be offloaded to anunlicensed radio frequency spectrum band, a carrier aggregation mode inwhich both LTE/LTE-A downlink and uplink communications may be offloadedfrom a licensed radio frequency spectrum band to an unlicensed radiofrequency spectrum band, and/or a standalone mode in which LTE/LTE-Adownlink and uplink communications between a base station 105 and a UE115 may take place in an unlicensed radio frequency spectrum band. Basestations 105 as well as UEs 115 may in some examples support one or moreof these or similar modes of operation. OFDMA waveforms may be used inthe communication links 125 for LTE/LTE-A downlink communications in alicensed radio frequency spectrum band and/or an unlicensed radiofrequency spectrum band, while OFDMA, SC-FDMA and/or resource blockinterleaved FDMA waveforms may be used in the communication links 125for LTE/LTE-A uplink communications in a licensed radio frequencyspectrum band and/or an unlicensed radio frequency spectrum band.

FIG. 2 shows a wireless communication system 200 in which LTE/LTE-A isdeployed under different scenarios using an unlicensed radio frequencyspectrum band, in accordance with various aspects of the presentdisclosure. More specifically, FIG. 2 illustrates examples of asupplemental downlink mode, a carrier aggregation mode, and a standalonemode in which LTE/LTE-A is deployed using an unlicensed radio frequencyspectrum band. The wireless communication system 200 may be an exampleof portions of the wireless communication system 100 described withreference to FIG. 1. Moreover, a first base station 205 and a secondbase station 205-a may be examples of aspects of one or more of the basestations 105 described with reference to FIG. 1, while a first UE 215, asecond UE 215-a, a third UE 215-b, and a fourth UE 215-c may be examplesof aspects of one or more of the UEs 115 described with reference toFIG. 1.

In the example of a supplemental downlink mode in the wirelesscommunication system 200, the first base station 205 may transmit OFDMAwaveforms to the first UE 215 using a downlink channel 220. The downlinkchannel 220 may be associated with a frequency F1 in an unlicensed radiofrequency spectrum band. The first base station 205 may transmit OFDMAwaveforms to the first UE 215 using a first bidirectional link 225 andmay receive SC-FDMA waveforms from the first UE 215 using the firstbidirectional link 225. The first bidirectional link 225 may beassociated with a frequency F4 in a licensed radio frequency spectrumband. The downlink channel 220 in the unlicensed radio frequencyspectrum band and the first bidirectional link 225 in the licensed radiofrequency spectrum band may operate concurrently. The downlink channel220 may provide a downlink capacity offload for the first base station205. In some examples, the downlink channel 220 may be used for unicastservices (e.g., addressed to one UE) or for multicast services (e.g.,addressed to several UEs). This scenario may occur with any serviceprovider (e.g., a mobile network operator (MNO)) that uses a licensedradio frequency spectrum and needs to relieve some of the traffic and/orsignaling congestion.

In one example of a carrier aggregation mode in the wirelesscommunication system 200, the first base station 205 may transmit OFDMAwaveforms to the second UE 215-a using a second bidirectional link 230and may receive OFDMA waveforms, SC-FDMA waveforms, and/or resourceblock interleaved FDMA waveforms from the second UE 215-a using thesecond bidirectional link 230. The second bidirectional link 230 may beassociated with the frequency F1 in the unlicensed radio frequencyspectrum band. The first base station 205 may also transmit OFDMAwaveforms to the second UE 215-a using a third bidirectional link 235and may receive SC-FDMA waveforms from the second UE 215-a using thethird bidirectional link 235. The third bidirectional link 235 may beassociated with a frequency F2 in a licensed radio frequency spectrumband. The second bidirectional link 230 may provide a downlink anduplink capacity offload for the first base station 205. Like thesupplemental downlink described above, this scenario may occur with anyservice provider (e.g., MNO) that uses a licensed radio frequencyspectrum and needs to relieve some of the traffic and/or signalingcongestion.

In another example of a carrier aggregation mode in the wirelesscommunication system 200, the first base station 205 may transmit OFDMAwaveforms to the third UE 215-b using a fourth bidirectional link 240and may receive OFDMA waveforms, SC-FDMA waveforms, and/or resourceblock interleaved waveforms from the third UE 215-b using the fourthbidirectional link 240. The fourth bidirectional link 240 may beassociated with a frequency F3 in the unlicensed radio frequencyspectrum band. The first base station 205 may also transmit OFDMAwaveforms to the third UE 215-b using a fifth bidirectional link 245 andmay receive SC-FDMA waveforms from the third UE 215-b using the fifthbidirectional link 245. The fifth bidirectional link 245 may beassociated with the frequency F2 in the licensed radio frequencyspectrum band. The fourth bidirectional link 240 may provide a downlinkand uplink capacity offload for the first base station 205. This exampleand those provided above are presented for illustrative purposes andthere may be other similar modes of operation or deployment scenariosthat combine LTE/LTE-A in licensed radio frequency spectrum and sharedaccess radio frequency spectrum for capacity offload.

As described above, one type of service provider that may benefit fromthe capacity offload offered by using LTE/LTE-A in shared access radiofrequency spectrum is a traditional MNO having access rights to anLTE/LTE-A licensed radio frequency spectrum band. For these serviceproviders, an operational example may include a bootstrapped mode (e.g.,supplemental downlink, carrier aggregation) that uses the LTE/LTE-Aprimary component carrier (PCC) on the licensed radio frequency spectrumband and at least one secondary component carrier (SCC) on theunlicensed radio frequency spectrum band.

In the carrier aggregation mode, data and control may, for example, becommunicated in the licensed radio frequency spectrum (e.g., via firstbidirectional link 225, third bidirectional link 235, and fifthbidirectional link 245) while data may, for example, be communicated inthe unlicensed radio frequency spectrum band (e.g., via secondbidirectional link 230 and fourth bidirectional link 240). The carrieraggregation mechanisms supported when using shared access radiofrequency spectrum may fall under a hybrid frequency divisionduplexing-time division duplexing (FDD-TDD) carrier aggregation or aTDD-TDD carrier aggregation with different symmetry across componentcarriers.

In one example of a standalone mode in the wireless communication system200, the second base station 205-a may transmit OFDMA waveforms to thefourth UE 215-c using a bidirectional link 250 and may receive OFDMAwaveforms, SC-FDMA waveforms, and/or resource block interleaved FDMAwaveforms from the fourth UE 215-c using the bidirectional link 250. Thebidirectional link 250 may be associated with the frequency F3 in theunlicensed radio frequency spectrum band. The standalone mode may beused in non-traditional wireless access scenarios, such as in-stadiumaccess (e.g., unicast, multicast). An example of a type of serviceprovider for this mode of operation may be a stadium owner, cablecompany, event host, hotel, enterprise, or large corporation that doesnot have access to a licensed radio frequency spectrum band.

In some examples, a transmitting apparatus such as one of the basestations 105, 205, and/or 205-a described with reference to FIGS. 1and/or 2, and/or one of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, may use a gating intervalto gain access to a channel of an unlicensed radio frequency spectrumband (e.g., to a physical channel of the unlicensed radio frequencyspectrum band). The gating interval may define the application of acontention-based protocol, such as an LBT protocol based on the LBTprotocol specified in European Telecommunications Standards Institute(ETSI) (EN 301 893). When using a gating interval that defines theapplication of an LBT protocol, the gating interval may indicate when atransmitting apparatus needs to perform a contention procedure, such asa clear channel assessment (CCA) procedure. The outcome of the CCAprocedure may indicate to the transmitting device whether a channel ofan unlicensed radio frequency spectrum band is available or in use forthe gating interval (also referred to as an LBT radio frame or a CCAframe). When a CCA procedure indicates that the channel is available(e.g., “clear” for use) for a corresponding LBT radio frame, thetransmitting apparatus may reserve and/or use the channel of theunlicensed radio frequency spectrum band during part or all of the LBTradio frame. When the CCA procedure indicates that the channel is notavailable (e.g., that the channel is in use or reserved by anotherapparatus), the transmitting apparatus may be prevented from using thechannel during the LBT radio frame.

In some cases, it may be useful for a transmitting apparatus to generatea gating interval on a periodic basis and synchronize at least oneboundary of the gating interval with at least one boundary of a periodicframe structure. For example, it may be useful to generate a periodicgating interval for a cellular downlink in an unlicensed radio frequencyspectrum band, and to synchronize at least one boundary of the periodicgating interval with at least one boundary of a periodic frame structure(e.g., a periodic LTE/LTE-A radio frame structure) associated with thecellular downlink. Examples of such synchronization are shown in FIG. 3.

FIG. 3 shows examples 300 of a gating interval (or LBT radio frame) fora cellular downlink in an unlicensed radio frequency spectrum band, inaccordance with various aspects of the present disclosure. A firstgating interval 305, a second gating interval 315, and/or a third gatinginterval 325 may be used as a periodic gating interval by an eNB or UEthat supports transmissions over the unlicensed radio frequency spectrumband. Examples of such an eNB may include the base stations 105, 205,and/or 205-a described with reference to FIGS. 1 and/or 2, and examplesof such a UE may include the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2. The first gating interval305, the second gating interval 315, and/or the third gating interval325 may in some examples be used with the wireless communication system100 and/or 200 described with reference to FIGS. 1 and/or 2.

By way of example, the duration of the first gating interval 305 isshown to be equal to (or approximately equal to) a duration of anLTE/LTE-A radio frame 310 of a periodic frame structure associated witha cellular downlink. In some examples, “approximately equal” means theduration of the first gating interval 305 is within a cyclic prefix (CP)duration of the duration of the periodic frame structure.

At least one boundary of the first gating interval 305 may besynchronized with at least one boundary of the periodic frame structurethat includes the LTE/LTE-A radio frames N−1 to N+1. In some cases, thefirst gating interval 305 may have boundaries that are aligned with theframe boundaries of the periodic frame structure. In other cases, thefirst gating interval 305 may have boundaries that are synchronizedwith, but offset from, the frame boundaries of the periodic framestructure. For example, the boundaries of the first gating interval 305may be aligned with subframe boundaries of the periodic frame structure,or with subframe midpoint boundaries (e.g., the midpoints of particularsubframes) of the periodic frame structure.

In some cases, the periodic frame structure may include LTE/LTE-A radioframes N−1 to N+1. Each LTE/LTE-A radio frame 310 may have a duration often milliseconds, for example, and the first gating interval 305 mayalso have a duration of ten milliseconds. In these cases, the boundariesof the first gating interval 305 may be synchronized with the boundaries(e.g., frame boundaries, subframe boundaries, or subframe midpointboundaries) of one of the LTE/LTE-A radio frames (e.g., the LTE/LTE-Aradio frame (N)).

By way of example, the durations of the second gating interval 315 andthe third gating interval 325 are shown to be sub-multiples of (orapproximate sub-multiples of) the duration of the periodic framestructure associated with the cellular downlink. In some examples, an“approximate sub-multiple of” means the duration of the second gatinginterval 315 and/or the third gating interval 325 is within a cyclicprefix (CP) duration of the duration of a sub-multiple of (e.g., half orone-fifth) the periodic frame structure. For example, the second gatinginterval 315 may have a duration of five milliseconds and the thirdgating interval 325 may have a duration of two milliseconds. The secondgating interval 315 or the third gating interval 325 may be advantageousover the first gating interval 305 because its shorter duration mayfacilitate more frequent sharing of an unlicensed radio frequencyspectrum band.

FIG. 4 shows an example 400 of a wireless communication 410 over anunlicensed radio frequency spectrum band, in accordance with variousaspects of the present disclosure. An LBT radio frame 415, which maycorrespond to a gating interval such as the first gating interval 305described with reference to FIG. 3, may have a duration of tenmilliseconds and include a number of downlink subframes 420, a number ofuplink subframes 425, and two types of special subframes, an S subframe430 and an S′ subframe 435. The S subframe 430 may provide a transitionbetween downlink subframes 420 and uplink subframes 425, while the S′subframe 435 may provide a transition between uplink subframes 425 anddownlink subframes 420. During the S′ subframe 435, a downlink clearchannel assessment (DCCA) procedure 440 may be performed by one or morebase stations, such as one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, to reserve, for aperiod of time, the channel over which the wireless communication 410occurs. Following a successful DCCA procedure 440 by a base station, thebase station may transmit a channel usage beacon signal (CUBS) 445 toprovide an indication to other base stations and/or apparatuses (e.g.,UEs, Wi-Fi access points, etc.) that the base station has reserved thechannel. In some examples, a CUBS 445 may be transmitted using aplurality of interleaved resource blocks. Transmitting a CUBS 445 inthis manner may enable the CUBS 445 to occupy at least a certainpercentage of the available frequency bandwidth in the unlicensed radiofrequency spectrum band and satisfy one or more regulatory requirements(e.g., a requirement that the CUBS 445 occupy at least 80% of theavailable frequency bandwidth). The CUBS 445 may in some examples take aform similar to that of an LTE/LTE-A cell-specific reference signal(CRS) and/or channel state information reference signal (CSI-RS).

The S′ subframe 435 may include 14 OFDM symbols, numbered 0 through 13in FIG. 4. A first portion of the S′ subframe 435, symbols 0 through 5in this example, may be used by base stations as a silent DL period,which may be required for compatibility with LTE/LTE-A communicationstandards. Thus, a base station may not transmit data during the silentDL period, although a UE may transmit some amount of uplink data duringthe silent DL period. A second portion of the S′ subframe 435 may beused for the DCCA procedure 440. In the example 400, the S′ subframe 435includes seven DCCA slots, included in symbols 6 through 12. Use of theDCCA slots by different network operators may be coordinated to providemore efficient system operation. In some examples, in order to determinewhich of the seven possible DCCA slots to use to perform a DCCAprocedure 440, a base station 105 may evaluate a mapping-function of theform:F _(D)(GroupID,t)∈{1,2,3,4,5,6,7}where GroupID is a “deployment group-id” assigned to the base station105, and t is the LBT radio frame number corresponding to a gatinginterval or frame for which the DCCA procedure 440 is performed.

FIG. 5 shows an example 500 of a wireless communication 510 over anunlicensed radio frequency spectrum band, in accordance with variousaspects of the present disclosure. An LBT radio frame 515, which maycorrespond to a gating interval such as the first gating interval 305described with reference to FIG. 3 and/or the LBT radio frame 415described with reference to FIG. 4, may have a duration of tenmilliseconds and include a number of downlink subframes 520, a number ofuplink subframes 525, and two types of special subframes (e.g., an Ssubframe 530 and an S′ subframe 535. The S subframe 530 may provide atransition between downlink subframes 520 and uplink subframes 525,while the S′ subframe 535 may provide a transition between uplinksubframes 525 and downlink subframes 520. During the S subframe 530, anuplink CCA (UCCA) procedure 540 may be performed by one or more UEs,such as one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed above with reference to FIGS. 1 and/or 2, to reserve, for aperiod of time, the channel over which the wireless communication 510occurs. Following a successful UCCA procedure 540 by a UE, the UE maytransmit a CUBS 545 to provide an indication to other UEs and/orapparatuses (e.g., base stations, Wi-Fi access points, etc.) that the UEhas reserved the channel. In some examples, a CUBS 545 may betransmitted using a plurality of interleaved resource blocks.Transmitting a CUBS 545 in this manner may enable the CUBS 545 to occupyat least a certain percentage of the available frequency bandwidth inthe unlicensed radio frequency spectrum band and satisfy one or moreregulatory requirements (e.g., a requirement that the CUBS 545 occupy atleast 80% of the available frequency bandwidth). The CUBS 545 may insome examples take a form similar to that of an LTE/LTE-A cell-specificreference signal (CRS) and/or channel state information reference signal(CSI-RS).

The S subframe 530 may include 14 OFDM symbols, numbered 0 through 13 inFIG. 5. A first portion of the S subframe 530, symbols 0 through 3 inthis example, may be used as a downlink pilot time slot (DwPTS) 550, anda second portion of the S subframe 530 may be used as a guard period(GP) 555. A third portion of the S subframe 530 may be used for UCCAprocedure 540. In the example 500, the S subframe 530 includes sevenUCCA slots, included in symbols 6 through 12. Use of the UCCA slots bydifferent UEs may be coordinated to provide more efficient systemoperation. In some examples, in order to determine which of the sevenpossible UCCA slots to use to perform a UCCA procedure 540, a UE mayevaluate a mapping-function of the form:F _(U)(GroupID,t)∈{1,2,3,4,5,6,7}where GroupID is a “deployment group-id” assigned to the UE, and t isthe LBT radio frame number corresponding to a frame for which a UCCAprocedure 540 is performed.

The mapping function for a DCCA procedure 440 and/or a UCCA procedure540 may be constructed based on different criteria, depending on whetherthe mapping function will have an orthogonalization or anon-orthogonalization property. In examples with orthogonal LBT access,the mapping function may have an orthogonalization property accordingto:F _(D/U)(x,t)≠F _(D/U)(y,t)GroupID x,y∈{1,2,3,4,5,6,7}for all time t, whenever x≠y represent different group-ids. In thiscase, base stations and/or UEs with different group-ids may perform CCAprocedures (e.g., DCCA procedures 440 and/or UCCA procedures 540) duringnon-overlapping CCA slots. In the absence of interference, the basestation or UE with the group-id which maps to an earlier CCA slot maysecure the channel for a period of time. According to variousdeployments, the mapping-function is fair, in the sense that acrossdifferent time indices t, the mapping {F_(D/U)(x, t), t=1, 2, 3, . . . }varies such that different group-ids have an equal chance of mapping toan earlier CCA slot (and hence secure the channel in the absence ofother interference) over a suitably long interval of time.

All base stations and UEs deployed by the same networkoperator/service-provider may be assigned the same group-id, so thatthey do not preempt each other in the contention process. This allowsfull frequency reuse among base stations and UEs of the same deployment,leading to enhanced system throughput. Base stations and/or UEs ofdifferent deployments may be assigned different group-ids, so that withorthogonal CCA slot mapping, access to the channel is mutuallyexclusive.

In examples with non-orthogonal, or overlapping, CCA slot access, themapping function may allow more than seven group ids. In somesituations, for example, it may be useful to support more than sevendeployment group-ids, in which case it is not possible to maintain theorthogonality property of CCA slot mapping functions. In such cases, itmay be desirable to reduce the frequency of collision between any twogroup-ids. In some examples, non-orthogonal CCA slot mapping sequencesmay also be used to provide fair channel access among deploymentswithout tight coordination on LBT opportunities. One example of anon-orthogonal CCA slot mapping sequence is given by:F _(D/U)(x,t)=R _(1,7)(x,t)GroupIDx=∈{1,2, . . . 2¹⁶}where R_(1,7)(x,t) is a pseudo-random number generator between 1 and 7chosen independently for GroupID x. In this case, there could bepotential collisions between base stations and/or UEs of differentGroupID's in the same LBT radio frame t.

Thus, CCA slots may be selected according to the noted mapping functionsand used for a DCCA procedure 440 and/or a UCCA procedure 540.

In each of FIGS. 4 and 5, the period between successful performance of aDCCA procedure 440 and the start of a transmission period for which theDCCA procedure 440 was performed (see, e.g., FIG. 4), or the periodbetween successful performance of a UCCA procedure 540 and the start ofa transmission period for which the UCCA procedure 540 was performed(see, e.g., FIG. 5), may be referred to as a preamble. Because ofvariability in when a DCCA procedure 440 or UCCA procedure 540 isperformed, the length of a preamble may vary. However, in each of theexamples shown in FIGS. 4 and 5, the preamble ends followingtransmission of the CUBS 445 (see, e.g., FIG. 4) or the CUBS 545 (see,e.g., FIG. 5).

FIG. 6 shows an example 600 of resource allocations for CCA-ExemptTransmissions (CETs) of synchronous operators in an unlicensed radiofrequency spectrum band, in accordance with various aspects of thepresent disclosure. A CET may be made without a need to perform a CCA(e.g., a DCCA or an uplink CCA (UCCA)) to first gain access to theunlicensed radio frequency spectrum band. Instead, an operator isexempted from performing a CCA for the purpose of transmitting a CET.

As shown, an allocation of resources 605 for CETs may be made, forexample, once every eighty milliseconds (80 ms) or once every CETperiod, where the CET period may have a configurable periodicity. Eachof a number of operators in the unlicensed radio frequency spectrum band(e.g., different PLMNs) may be provided a separate subframe (shown) orsubframes (not shown) for transmitting CETs. By way of example, FIG. 6shows adjacent CET subframes for seven different operators (e.g.,operators PLMN1, PLMN2, . . . , PLMN7). Such a CET transmissionframework may be applicable to a downlink and/or uplink between a basestation and a UE.

In some examples of an LBT-LBE protocol, a transmitting apparatus mayperform a CCA procedure and, when the CCA procedure is successful,immediately begin transmitting over a channel of an unlicensed radiofrequency spectrum band. However, when the CCA procedure isunsuccessful, the transmitting apparatus may perform an extended CCAprocedure by selecting a random integer, N, between 1 and q, where q hasa value of 4≤q≤32 advertised by an operator or vendor. Upon selecting avalue for the random integer, N, the transmitting apparatus may wait toaccess an unlicensed radio frequency spectrum band for N CCA procedureswhere a channel of the unlicensed radio frequency spectrum band is foundto be clear. Upon the channel of the unlicensed radio frequency spectrumband being found clear for the N CCA procedures, the transmittingapparatus may transmit over the unlicensed radio frequency spectrum bandfor at most ( 13/32)×q milliseconds (msec) before needing to performanother extended CCA procedure. The ( 13/32)×q msec transmission time istherefore a maximum channel occupancy time (i.e.,MaxChannelOccupancyTime). Upon receiving a transmission from thetransmitter, a receiver may immediately begin anacknowledgement/non-acknowledgement (ACK/NAK) transmission, provided thelast successful CCA procedure or extended CCA procedure was performedless than MaxChannelOccupancyTime ago.

Under most conditions, the use of an LBT-FBE protocol by a transmittingapparatus provides sufficient access to an unlicensed radio frequencyspectrum band. The use of an LBT-FBE protocol can be advantageous inthat it enables frequency reuse 1 among base stations or eNBs associatedwith the same operator. However, under some scenarios, one or more Wi-Finodes may prevent an LTE/LTE-A node from accessing a channel of anunlicensed radio frequency spectrum band. In these scenarios, use of anLBT-LBE protocol may be advantageous over an LBT-FBE protocol (despitethe fact that use of an LBT-LBE protocol may prevent frequency reuse 1under some conditions), in that a transmitting apparatus maypersistently attempt to access the unlicensed radio frequency spectrumband when employing an LBT-LBE protocol. For example, the transmittingapparatus may attempt to access the medium for a random duration of NCCA procedures, but for a maximum duration controlled by the parameterq. A smaller value of q implies a shorter maximum extended CCA procedureduration and shorter radio frame length. One disadvantage of an LBT-LBEprotocol compared to an LTB-FBE protocol is that the random integer, N,on which an extended CCA procedure is based provides for asynchronousoperation of a plurality of transmitters, potentially leading toinefficient operation (e.g., dimension loss).

A transmitting apparatus capable of using an LBT-FBE protocol under mostconditions, and an LBT-LBE protocol when necessary, may be useful insome wireless communication systems. Such a transmitting apparatus mayuse a same or similar LBT radio frame structure when using either theLBT-FBE protocol or the LBT-LBE protocol, but may use somewhat differentCCA procedures for the different protocols. In some examples, thedifferences in CCA procedures (e.g., access procedures) used by anLBT-LBE protocol and an LBT-FBE protocol may not be defined in 3GPPspecifications, but rather in a corresponding ETSI document.

FIG. 7 shows a timing diagram 700 of wireless communications over anunlicensed radio frequency spectrum band, in accordance with variousaspects of the present disclosure. In some examples, the unlicensedradio frequency spectrum band may be a radio frequency spectrum band forwhich apparatuses may need to contend for access because the radiofrequency spectrum band is available, at least in part, for unlicenseduse (e.g., Wi-Fi use and/or LTE/LTE-A use in an unlicensed radiofrequency spectrum band).

By way of example, the wireless communications shown in FIG. 7 includecommunications (or transmissions (Tx)) by an Operator 1, an Operator 2,and a Wi-Fi node. By way of further example, transmitters of Operator 1and Operator 2, as well as the Wi-Fi node, may be within CCA range ofeach other. Operator 1 may transmit a CCA-Exempt Transmission (CET) 705over the unlicensed radio frequency spectrum band, followed by a firstnumber of radio frames (e.g., radio frames FR_01, FR_11, FR_21, and/orFR_31). Operator 2 may transmit a CET 710 over the unlicensed radiofrequency spectrum band, followed by a second number of radio frames(e.g., radio frames FR_02 and/or FR_12). The Wi-Fi node may alsotransmit over the unlicensed radio frequency spectrum band (e.g., thetransmission labeled Wi-Fi). When a transmitter associated with Operator1 is transmitting over a channel of the unlicensed radio frequencyspectrum band, Operator 2 and the Wi-Fi node may be prevented fromaccessing the channel of the unlicensed radio frequency spectrum band.When a transmitter associated with Operator 2 is transmitting over achannel of the unlicensed radio frequency spectrum band, transmitters ofOperator 1 and the Wi-Fi node may be prevented from accessing thechannel of the unlicensed radio frequency spectrum band. When the Wi-Finode is transmitting over a channel of the unlicensed radio frequencyspectrum band, transmitters associated with Operator 1 and Operator 2may be prevented from accessing the channel of the unlicensed radiofrequency spectrum band.

In some examples, the transmitters of Operator 1 and Operator 2 may gainaccess to the unlicensed radio frequency spectrum band (or a channelthereof) by performing an extended CCA procedure labeled NxCCA. Accessis only gained when an extended CCA procedure is successful (labeled asExt CCA Success).

In some examples, each radio frame transmitted by Operator 1 or Operator2 may be an LTE/LTE-A radio frame having 10 subframes and a duration of10 msec. Each subframe may include, for example, fourteen OFDM symbols.The subframes may variously include data subframes, uplink subframes, orspecial subframes (e.g., subframes used to transmit control information,synchronization signals, some data, etc.).

The use of an LBT-LBE protocol (e.g., operation in an LBT-LBE mode ofoperation over an unlicensed radio frequency spectrum band) does notnecessarily impact radio resource management (RRM) measurements, becausethe measurements can be performed on a CET transmitted by a transmittingapparatus. However, with respect to reference and control channeltransmissions, the reference and control channel transmissions over anunlicensed radio frequency spectrum band may be defined based on thestart (e.g., a frame boundary) of an LBT radio frame. Thus, the use ofan LBT-LBE protocol can impact higher layer control signaling design,such as the configuration of channel state information (CSI) resources.This may be addressed (when using either an LBT-LBE protocol or anLBT-FBE protocol) by transmitting a signal to convey locationinformation of overhead signals in relation to the timing of a radioframe boundary. In some examples, the signal to convey locationinformation of overhead signals in relation to the timing of a radioframe boundary may include radio resource control (RRC) signaling. Insome examples, the signal to convey location information of overheadsignals in relation to the timing of a radio frame boundary may conveylocation information for a downlink control channel in relation to theradio frame boundary and/or location information for resources used forCSI feedback. In some examples, the signal to convey locationinformation of overhead signals in relation to the timing of a radioframe boundary may be provided in a CUBS and/or a CUBS may include thedownlink control channel, information indicating a CSI configuration,and/or the resources used for CSI feedback.

When using an LBT-LBE protocol, it may be useful to transmit downlinkgrants on a secondary serving cell (e.g., over an unlicensed radiofrequency spectrum band, with data on an enhanced physical downlinkcontrol channel (EPDCCH) or on a new control channel), because crosscarrier scheduling may be problematic due to a possible lack of subframealignment between a primary serving cell and the secondary serving cell.

In some examples, a UE operating under an LBT protocol may detect a basestation or eNB discovery signal (e.g., a primary synchronization signal(PSS), a secondary synchronization signal (SSS), and/or a dedicatedreference signal (DRS)) in a CET transmitted by the base station or eNB.Upon detecting the discovery signal, the UE may assume an OFDM symbolperiod timing based on the detected discovery signal. When operatingunder an LBT-FBE protocol, subframe timing may not differ from one LBTframe to another. However, subframe timing may in some cases differ fromone LBT radio frame to another when operating under an LBT-LBE protocol.A UE capable of operating under either of an LBT-FBE protocol or anLBT-LBE protocol may therefore not assume subframe or frame timing basedon the detection of a discovery signal.

In some examples of the wireless communication system 100 and/or 200described with reference to FIGS. 1 and/or 2, it may be desirable to usea preamble such as the preamble described with reference to FIGS. 4and/or 5 to transmit information (e.g., N bits of information) over achannel in a radio frequency spectrum band. For example, the informationmay be transmitted with a signal that indicates accessing (e.g., thereserving of) a channel in the radio frequency spectrum band. In someexamples, the signal that indicates accessing the channel in the radiofrequency spectrum band may include a CUBS such as the CUBS 445 and/or545 described with reference to FIGS. 4 and/or 5.

The transmitted information may include various types of information. Insome examples, the information may include a cell identifier (ID), apublic land mobile network (PLMN) ID, or a combination thereof. In someexamples, the information may indicate a frame structure fortransmission in the radio frequency spectrum band (e.g., the LBT radioframe duration). In some examples, the information may indicate a numberof subframes and/or symbols that will be used for transmission in aframe structure in the radio frequency spectrum band (e.g., fivesubframes are used for transmission in a ten millisecond frame durationthat includes ten subframes). An indication of a number of subframesand/or symbols that will be used for transmission in a frame structurein the radio frequency spectrum band may enable a receiving apparatus,such as a UE, to enter a low power state at an earlier time (e.g.,immediately after receiving the transmitted subframes), therebyconserving power. In some examples, the information may indicate anuplink configuration and/or a downlink configuration for transmission inthe radio frequency spectrum band (e.g., an uplink configuration and/ora downlink configuration of a frame structure in the radio frequencyspectrum band). An indication of an uplink configuration and/or adownlink configuration for transmission in the radio frequency spectrumband may improve the performance of enhanced Interference Mitigation &Traffic Adaptation (eIMTA) functionality. In some examples, theinformation may indicate whether a maximum number of subframes, of aframe, are used for transmission in the radio frequency spectrum band(e.g., a single bit may be used to indicate whether a maximum number ofsubframes are used for transmission in a frame structure of the radiofrequency spectrum band, or whether fewer than the maximum number ofsubframes are used for transmission in the frame structure of the radiofrequency spectrum band). In some examples, the information may indicatea number of antennas to use for receiving a transmission carried on acomponent carrier in the radio frequency spectrum band. The informationmay also or alternatively include any combination of the above types ofinformation and/or other types of information, including other types ofsystem information.

In some examples, information may be transmitted with a signal thatindicates accessing a channel in the radio frequency spectrum band bytransmitting the information as part of the signal that indicatesaccessing the channel in the radio frequency spectrum band (e.g., aspart of a CUBS). In these examples, the CUBS, for example, may begenerated based at least in part on a sequence. The sequence may be afunction of the information to be transmitted. For example, the sequencemay be a function of a cell ID, a PLMN ID, or a combination thereof. Thesequence may also or alternatively be a function of any one orcombination of the types of information referenced herein.

In other examples in which the information is transmitted as part of asignal that indicates accessing a channel in the radio frequencyspectrum band (e.g., as part of a CUBS), the information may betransmitted by selecting a phase from among a plurality of phases fortransmission of the signal. The selected phase may correspond to theinformation to be transmitted, whereas other phases in the plurality ofphases may correspond to different information. In another example,different phase offsets between a plurality of signals that indicateaccessing a channel in the radio frequency spectrum band may correspondto different information to be transmitted.

In some examples, information may be transmitted with a signal (e.g., aCUBS) that indicates accessing a channel in the radio frequency spectrumband by transmitting the information in a second signal, which secondsignal may be transmitted along with the signal that indicates accessinga channel in the radio frequency spectrum band. In some examples, thesecond signal may be interleaved with, or transmitted adjacent to, thesignal that indicates accessing a channel in the radio frequencyspectrum band, as described with reference to FIG. 8.

FIG. 8A shows an example 800 of how information may be transmitted witha first signal 805 (e.g., a CUBS) that indicates accessing a channel ina radio frequency spectrum band, in accordance with various aspects ofthe present disclosure.

As shown, the first signal 805 may be transmitted as a plurality oftones (e.g., a first tone 805-a, a second tone 805-b, a third tone805-c, a fourth tone 805-d, a fifth tone 805-e, a sixth tone 805-f, aseventh tone 805-g, and/or an eighth tone 805-h) using a first pluralityof interleaved resource blocks in the frequency domain. In someexamples, the first signal 805 may be transmitted using more, fewer,and/or different tones. Transmitting the first signal 805 in this mannermay enable the first signal 805 to occupy at least a certain percentageof the available frequency bandwidth in the radio frequency spectrumband and satisfy one or more regulatory requirements (e.g., arequirement that the first signal 805 occupy at least 80% of theavailable frequency bandwidth). The first signal 805 may in someexamples take a form similar to that of an LTE/LTE-A cell-specificreference signal (CRS) and/or channel state information reference signal(CSI-RS).

The information may be transmitted in a second signal 810. The secondsignal 810 may also be transmitted as a plurality of tones (e.g., aninth tone 810-a, a tenth tone 810-b, an eleventh tone 810-c, a twelfthtone 810-d, a thirteenth tone 810-e, a fourteenth tone 810-f, afifteenth tone 810-g, and/or a sixteenth tone 810-h) using a secondplurality of interleaved resource blocks in the frequency domain. Insome examples, the second signal 810 may be transmitted using more,fewer, and/or different tones. The second signal 810 may in someexamples take a form similar to that of an LTE/LTE-A physical controlformat indicator channel (PCFICH).

As shown, the first signal 805 and the second signal 810 may betransmitted during a single OFDM symbol period of the radio frequencyspectrum band. The first signal 805 may provide automatic gain control(AGC) information for the second signal 810.

FIG. 8B shows an example 850 of how information may be transmitted witha first signal 855 (e.g., a CUBS) that indicates accessing a channel ina radio frequency spectrum band, in accordance with various aspects ofthe present disclosure.

As shown, the first signal 855 may be transmitted as a plurality oftones (e.g., a first tone 855-a, a second tone 855-b, a third tone855-c, a fourth tone 855-d, a fifth tone 855-e, a sixth tone 855-f, aseventh tone 855-g, an eighth tone 855-h, a ninth tone 855-i, aneleventh tone 855-j, a twelfth tone 855-k, a thirteenth tone 855-l, afourteenth tone 855-m, a fifteenth tone 855-n, and/or a sixteenth tone855-o) over a plurality of OFDM symbol periods (e.g., two OFDM symbolperiods). In some examples, the first signal 855 may be transmittedusing more, fewer, and/or different tones. Transmitting the first signal855 in this manner may enable the first signal 855 to occupy at least acertain percentage of the available frequency bandwidth in the radiofrequency spectrum band and/or satisfy one or more regulatoryrequirements (e.g., a requirement that the first signal 855 occupy atleast 80% of the available frequency bandwidth). The first signal 855may in some examples take a form similar to that of an LTE/LTE-Acell-specific reference signal (CRS) and/or channel state informationreference signal (CSI-RS).

The information may be transmitted in a second signal 860. The secondsignal 860 may also be transmitted as a plurality of tones (e.g., aseventeenth tone 860-a, an eighteenth tone 860-b, a nineteenth tone860-c, a twentieth tone 860-d, a twenty-first tone 860-e, atwenty-second tone 860-f, a twenty-third tone 860-g, and/or atwenty-fourth tone 860-h) using a second plurality of interleavedresource blocks in the frequency domain. In some examples, the secondsignal 860 may be transmitted using more, fewer, and/or different tones.The second signal 860 may in some examples take a form similar to thatof an LTE/LTE-A physical control format indicator channel (PCFICH).

As shown, the first signal 855 may be transmitted during a first OFDMsymbol period of the radio frequency spectrum band and a second OFDMsymbol period of the radio frequency spectrum band, and the secondsignal 860 may be transmitted during the second OFDM symbol period ofthe radio frequency spectrum band. In some examples, the first OFDMsymbol period of the radio frequency spectrum band and the second OFDMsymbol period of the radio frequency spectrum band may be adjacent OFDMsymbol periods (as shown). The first signal 855 may provide AGCinformation and/or a phase reference for the second signal 860.

FIG. 9 shows an example 900 of how information indicating a number ofantennas to use for receiving a transmission carried on a componentcarrier may be determined and used, in accordance with various aspectsof the present disclosure. More particularly, FIG. 9 shows an LBT radioframe 915 (or gating interval) for transmission of a first componentcarrier (CC1) and a second component carrier (CC2) in an unlicensedradio frequency spectrum band. Upon a base station winning contention toaccess the first component carrier CC1 and/or the second componentcarrier CC2, the base station may transmit a signal indicating accessingthe first component carrier CC1 and/or the second component carrier CC2in the unlicensed radio frequency spectrum band to a UE. In someexamples, the base station may be an example of one or more aspects ofthe base station 105, 205, and/or 205-a described with reference toFIGS. 1 and/or 2, and/or the UE may be an example of one or more aspectsof the UE 115, 215, 215-a, 215-b, and/or 215-c described with referenceto FIGS. 1 and/or 2.

By way of example, each of the first component carrier CC1 and thesecond component carrier CC2 may have a frame structure similar to theframe structure shown in FIG. 4. For example, the frame structure ofeach of the first component carrier CC1 and the second component carrierCC2 may include a number of downlink subframes 920 or 925, a number ofuplink subframes 930 or 935, and two types of special subframes, an Ssubframe 940 or 945, and an S′ subframe 950 or 955. The S subframe 940or 945 may provide a transition between downlink subframes 920 or 925and uplink subframes 930 or 935, while the S′ subframe 950 or 955 mayprovide a transition between uplink subframes 930 or 935 and downlinksubframes 920 or 925. In other examples, one or both of the firstcomponent carrier CC1 and the second component carrier CC2 may have aframe structure that differs more substantially from the frame structureshown in FIG. 4.

During the S′ subframes 950 and 955, a base station may perform a firstDCCA procedure 905 (e.g., a first contention procedure) to contend foraccess to the first component carrier CC1 in an unlicensed radiofrequency spectrum band during the LBT radio frame 915. Similarly, thebase station may perform a second DCCA procedure 910 (e.g., a secondcontention procedure) to contend for access to the second componentcarrier CC2 in an unlicensed radio frequency spectrum band during theLBT radio frame 915. After winning contention to transmit both the firstcomponent carrier CC1 and the second component carrier CC2 during theLBT radio frame 915 (not shown), the base station may transmit data onboth the first component carrier CC1 and the second component carrierCC2 to a UE in the unlicensed radio frequency spectrum band. By way ofexample, the transmission of data on the first component carrier CC1 bythe base station may employ two antennas of the base station, and thetransmission of data on the second component carrier CC2 may employadditional two antennas of the base station. Similarly, the UE receivingthe transmission carried on the first component carrier CC1 and thesecond component carrier CC2 in the unlicensed radio frequency spectrumband may employ two antennas to receive the transmission carried on thefirst component carrier CC1 and employ additional two antennas toreceive the transmission carried on the second component carrier CC2. Insome examples, the UE may reserve the two antennas for receiving thetransmission carried on the first component carrier CC1 during the LBTradio frame 915, and reserve the additional two antennas for receivingthe transmission carried on the second component carrier CC2 during theLBT radio frame 915, without knowing whether the first component carrierCC1 and/or the second component carrier CC2 will carry a transmissionduring the LBT radio frame 915.

By way of example, FIG. 9 illustrates a scenario in which the first DCCAprocedure 905 results in failure to win contention to access to thefirst component carrier CC1, and the second DCCA procedure 910 resultsin winning contention to access the second component carrier CC2.Assuming that a UE to which a base station transmits data on the secondcomponent carrier CC2 in the unlicensed radio frequency spectrum bandhas reserved two antennas for receiving data on the first componentcarrier CC1 during the LBT radio frame 915, and has reserved anadditional two antennas for receiving data on the second componentcarrier CC2 during the LBT radio frame 915, the two antennas reserved bythe UE for receiving data on the first component carrier CC1 may gounused during the LBT radio frame 915. However, if the base station cantransmit information indicating a number of antennas to use forreceiving a transmission carried on the first component carrier CC1and/or the second component carrier CC2, the UE may be able to employthe two antennas reserved to receive data on the first component carrierCC1 to receive data on the second component carrier CC2 during part orall of the LBT radio frame 915. Thus, for example, the base station mayindicate to the UE to use four antennas 965 to receive a transmission ofdata carried on the second component carrier CC2 during the LBT radioframe 915.

The base station may, in some examples, transmit information to the UEwith a CUBS 960. The transmitted information may include the indicationto use four antennas 965 for receiving a transmission carried on thesecond component carrier CC2 during the LBT radio frame 915. In otherexamples, the UE may autonomously determine a number of antennas to usefor receiving a transmission carried on the first component carrier CC1and/or the second component carrier CC2. The autonomous determinationmay be based, for example, on a UE autonomous determination of whetherthe base station won contention to access the first component carrierCC1 and/or the second component carrier CC2 (e.g., based on thedetection of a CUBS transmitted over each of the first component carrierCC1 and/or the second component carrier CC2).

In some examples, when the number of antennas to use for receiving atransmission carried on a component carrier is adjusted, a precodingmatrix, a rank, and/or a modulation and coding scheme (MCS) for a datatransmission carried on the component carrier may be adjusted based atleast in part on the number of antennas to use for receiving thetransmission carried on the component carrier in a radio frequencyspectrum band. In some examples, an increase in the number of antennasto use for receiving a transmission carried on a component carrier mayenable an increase in the MCS, and consequently, an increase in the datarate.

FIG. 10 shows an example 1000 of how information indicating a number ofantennas to use for receiving a transmission carried on a componentcarrier may be determined and used, in accordance with various aspectsof the present disclosure. More particularly, FIG. 10 shows an LBT radioframe 1015 (or gating interval) for transmission of a first componentcarrier (CC1) and a second component carrier (CC2) in an unlicensedradio frequency spectrum band. Upon a base station winning contention toaccess the first component carrier CC1 and/or the second componentcarrier CC2, the base station may transmit a signal indicating access tothe first component carrier CC1 and/or the second component carrier CC2in the unlicensed radio frequency spectrum band to a UE. In someexamples, the base station may be an example of one or more aspects ofthe base station 105, 205, and/or 205-a described with reference toFIGS. 1 and/or 2, and/or the UE may be an example of one or more aspectsof the UE 115, 215, 215-a, 215-b, and/or 215-c described with referenceto FIGS. 1 and/or 2.

By way of example, each of the first component carrier CC1 and thesecond component carrier CC2 may have a frame structure similar to theframe structure shown in FIG. 4. For example, the frame structure ofeach of the first component carrier CC1 and the second component carrierCC2 may include a number of downlink subframes 1020 or 1025, a number ofuplink subframes 1030 or 1035, and two types of special subframes, an Ssubframe 1040 or 1045, and an S′ subframe 1050 or 1055. The S subframe1040 or 1045 may provide a transition between downlink subframes 1020 or1025 and uplink subframes 1030 or 1035, while the S′ subframe 1050 or1055 may provide a transition between uplink subframes 1030 or 1035 anddownlink subframes 1020 or 1025. In other examples, one or both of thefirst component carrier CC1 and the second component carrier CC2 mayhave a frame structure that differs more substantially from the framestructure shown in FIG. 4.

During the S′ subframes 1050 and 1055, a base station may perform afirst DCCA procedure 1005 (e.g., a first contention procedure) tocontend for access to the first component carrier CC1 in an unlicensedradio frequency spectrum band during the LBT radio frame 1015.Similarly, the base station may perform a second DCCA procedure 1010(e.g., a second contention procedure) to contend for access to thesecond component carrier CC2 in an unlicensed radio frequency spectrumband during the LBT radio frame 1015. When winning contention totransmit both the first component carrier CC1 and the second componentcarrier CC2 during the LBT radio frame 1015, the base station maytransmit data on both the first component carrier CC1 and the secondcomponent carrier CC2 to a UE in the unlicensed radio frequency spectrumband. By way of example, and because the base station transmits downlinksubframes 1020 and 1025 in subframes SF0, SF1, and SF2 of both the firstcomponent carrier CC1 and the second component carrier CC2, thetransmission of data on the first component carrier CC1 by the basestation may employ two antennas of the base station during thetransmission of subframes SF0, SF1, and SF2 of the LBT radio frame 1015,and the transmission of data on the second component carrier CC2 mayemploy additional two antennas of the base station during thetransmission of subframes SF0, SF1, and SF2 of the LBT radio frame 1015.Similarly, the UE receiving the transmission carried on the firstcomponent carrier CC1 and the second component carrier CC2 in theunlicensed radio frequency spectrum band during the subframes SF0, SF1,and SF2 may employ two antennas 1070 to receive the transmission carriedon the first component carrier CC1 and additional two antennas 1075 toreceive the transmission carried on the second component carrier CC2.However, because the uplink and downlink configurations of the firstcomponent carrier CC1 and the second component carrier CC2 are such thatsubframes SF3 and SF4 of the second component carrier CC2 do not carrydownlink transmissions, the transmission of data on the first componentcarrier CC1 by the base station may employ four antennas of the basestation during the transmission of subframes SF3 and SF4 of the LBTradio frame 1015. Similarly, the UE receiving the transmission carriedon the first component carrier CC1 and the second component carrier CC2in the unlicensed radio frequency spectrum band during the subframes SF3and SF4 may employ four antennas 1080 to receive the transmission of thefirst component carrier CC1. The four antennas 1080 may include theadditional two antennas 1075 that were used to receive the secondcomponent carrier CC2 during the subframes SF0, SF1, and SF2 of the LBTradio frame 1015.

The base station may in some examples transmit information indicating anumber of antennas to use for receiving a transmission carried on thefirst component carrier CC1 and/or the second component carrier CC2. Theinformation may in some examples be based on an uplink configurationand/or a downlink configuration of the first component carrier CC1and/or the second component carrier CC2. In the scenario shown in FIG.10, the information may indicate to the UE to use four antennas 1080 forreceiving a transmission of data on the first component carrier CC1during subframes SF3 and SF4 of the LBT radio frame 1015.

The base station may, in some examples, transmit information to the UEwith a first CUBS 1060 following the successful first DCCA procedure1005 and/or a second CUBS 1065 following the successful second DCCAprocedure 1010. The transmitted information may include the indicationto use the four antennas 1080 for receiving a transmission of data onthe first component carrier CC1 during subframes SF3 and SF4 of the LBTradio frame 1015. In other examples, the UE may autonomously determine anumber of antennas to use for receiving a transmission carried on thefirst component carrier CC1 and/or the second component carrier CC2. Theautonomous determination may be based, for example, on a UE autonomousdetermination of whether the base station won contention to access thefirst component carrier CC1 and/or the second component carrier CC2(e.g., based on the detection of a CUBS transmitted over each of thefirst component carrier CC1 and/or the second component carrier CC2)and/or the uplink and downlink configurations of the first componentcarrier CC1 and/or the second component carrier CC2.

In some examples, when the number of antennas to use for receiving atransmission carried on a component carrier is adjusted, a precodingmatrix, a rank, and/or an MCS for a data transmission over the componentcarrier may be adjusted based at least in part on the number of antennasto use to receive the component carrier in a radio frequency spectrumband. In some examples, an increase in the number of antennas to use forreceiving a transmission carried on a component carrier may enable anincrease in the MCS, and consequently, an increase in the data rate.

In some examples of the wireless communication system 100 and/or 200described with reference to FIGS. 1 and/or 2, a successful contentionprocedure (e.g., a DCCA procedure, extended DCCA procedure, UCCAprocedure, or extended UCCA procedure) may conclude before a boundary ofa next OFDM symbol period. When an apparatus wins contention to a radiofrequency spectrum band during the contention procedure, it may bedesirable to transmit a signal over the radio frequency spectrum band.The signal may be used to reserve the radio frequency spectrum bandduring the time between conclusion of the contention procedure and thestart of the next OFDM symbol period. In some examples, the commencementof such a signal may not coincide with a boundary of an OFDM symbolperiod, slot, subframe, or other reference boundary, and the length ofsuch a signal may be variable due to variances between the timing ofwhen a contention procedure successfully concludes and the timing of areference boundary following the successful conclusion of the contentionprocedure. FIGS. 11A, 11B, and 11C, 12, 13, 14, and 15 illustrateexamples of such a signal.

FIG. 11A shows an example 1100 of how a first signal may be transmittedto align a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure. More particularly, FIG. 11Ashows a plurality of OFDM symbol periods bounded by a plurality of OFDMsymbol period boundaries 1105. The OFDM symbol periods may include afirst OFDM symbol period 1110 in which a DCCA procedure 1120 (e.g., aDCCA procedure similar to the DCCA procedure 440 described withreference to FIG. 4) may be performed. The OFDM symbol periods may alsoinclude a second OFDM symbol period 1115 in which a signal 1125 toindicate accessing the radio frequency spectrum band (e.g., a CUBSsimilar to the CUBS 445 described with reference to FIG. 4) may betransmitted.

In some examples, the DCCA procedure 1120 may be performed at a variabletime within the first OFDM symbol period 1110. In some examples, a basestation may perform the DCCA procedure 1120, and win contention toaccess the radio frequency spectrum band, prior to a reference boundary(e.g., the OFDM symbol period boundary 1130) associated with the radiofrequency spectrum band. In these examples, the base station maytransmit a first signal 1135 (e.g., a variable length training sequenceincluding a first unit training signal 1135-a, a second unit trainingsignal 1135-b, and a third unit training signal 1135-c) to align astarting point of a second signal (e.g., a starting point of the CUBS1125) with the reference boundary.

In some examples, information as discussed above may be transmitted aspart of the first signal 1135 (e.g., as part of the first unit trainingsignal 1135-a, the second unit training signal 1135-b, and/or the thirdunit training signal 1135-c). In some examples, the first signal 1135(e.g., the first unit training signal 1135-a, the second unit trainingsignal 1135-b, and/or the third unit training signal 1135-c) may beusable for AGC by a UE.

In some examples, the first signal 1135 may be associated with acontention priority (e.g., a priority with which the DCCA procedure 1120is performed), and the first signal 1135 may be transmitted during aportion of the first OFDM symbol period 1110 based at least in part onthe contention priority. For example, a base station having a class oftraffic or transmission with a higher priority may be configured tocontend for access to a radio frequency spectrum band at an earlierportion of the first OFDM symbol period 1110 than a base station havinga class of traffic or transmission with a lower priority. The first OFDMsymbol period 1110 may provide relatively more or relatively fewer slotsfor performing DCCA procedures, and in some examples, slots forperforming DCCA procedures may be provided over more than one OFDMsymbol period. More slots for performing DCCA procedures translates tomore control over the contention priorities of different base stations.

FIG. 11B shows an example 1150 of how a first signal may be transmittedto align a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure. More particularly, FIG. 11Bshows a plurality of OFDM symbol periods bounded by a plurality of OFDMsymbol period boundaries 1105. The OFDM symbol periods may include afirst OFDM symbol period 1110 in which a DCCA procedure 1155 (e.g., aDCCA procedure similar to the DCCA procedure 440 described withreference to FIG. 4) may be performed. The OFDM symbol periods may alsoinclude a second OFDM symbol period 1115 in which a signal 1125 toindicate accessing the radio frequency spectrum band (e.g., a CUBSsimilar to the CUBS 445 described with reference to FIG. 4) may betransmitted.

In some examples, the DCCA procedure 1155 may be performed at a variabletime within the first OFDM symbol period 1110. In some examples, a basestation may perform the DCCA procedure 1155, and win contention toaccess the radio frequency spectrum band, prior to a reference boundary(e.g., the OFDM symbol period boundary 1130) associated with the radiofrequency spectrum band. In these examples, the base station maytransmit a first signal 1135 (e.g., a variable length training sequenceincluding a first unit training signal 1135-b and a second unit trainingsignal 1135-c) to align a starting point of a second signal (e.g., astarting point of the CUBS 1125) with the reference boundary. Becausethe timing of the DCCA procedure 1155 performed in the example 1150 islater within the first OFDM symbol period 1110 than the timing of theDCCA procedure 1120 performed in the example 1100, the length of thefirst signal described with reference to FIG. 11B may be shorter thanthe length of the first signal described with reference to FIG. 11A.

In some examples, information as discussed above may be transmitted aspart of the first signal 1135 (e.g., as part of the first unit trainingsignal 1135-b and/or the second unit training signal 1135-c). In someexamples, the first signal 1135 (e.g., the first unit training signal1135-b and/or the second unit training signal 1135-c) may be usable forAGC by a UE.

In some examples, the first signal 1135 may be associated with acontention priority (e.g., a priority with which the DCCA procedure 1155is performed), and the first signal 1135 may be transmitted during aportion of the first OFDM symbol period 1110 based at least in part onthe contention priority. For example, a base station having a class oftraffic or transmission with a higher priority may be configured tocontend for access to a radio frequency spectrum band at an earlierportion of the first OFDM symbol period 1110 than a base station havinga class of traffic or transmission with a lower priority. The first OFDMsymbol period 1110 may provide relatively more or relatively fewer slotsfor performing DCCA procedures, and in some examples, slots forperforming DCCA procedures may be provided over more than one OFDMsymbol period. More slots for performing DCCA procedures translates tomore control over the contention priorities of different base stations.

FIG. 11C shows an example 1170 of how a first signal may be transmittedto align a starting point of a second signal with a reference boundaryassociated with a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure. More particularly, FIG. 11Cshows a plurality of OFDM symbol periods bounded by a plurality of OFDMsymbol period boundaries 1105. The OFDM symbol periods may include afirst OFDM symbol period 1110 in which a DCCA procedure 1175 (e.g., aDCCA procedure similar to the DCCA procedure 440 described withreference to FIG. 4) may be performed. The OFDM symbol periods may alsoinclude a second OFDM symbol period 1115 in which a signal 1125 toindicate accessing the radio frequency spectrum band (e.g., a CUBSsimilar to the CUBS 445 described with reference to FIG. 4) may betransmitted.

In some examples, the DCCA procedure 1175 may be performed at a variabletime within the first OFDM symbol period 1110. In some examples, a basestation may perform the DCCA procedure 1175, and win contention toaccess the radio frequency spectrum band, prior to a reference boundary(e.g., the OFDM symbol period boundary 1130) associated with the radiofrequency spectrum band. In these examples, the base station maytransmit a first signal 1135 (e.g., a variable length training sequenceincluding a unit training signal 1135-c) to align a starting point of asecond signal (e.g., a starting point of the CUBS 1125) with thereference boundary. Because the timing of the DCCA procedure 1175performed in the example 1170 is later within the first OFDM symbolperiod 1110 than the timing of the DCCA procedure 1120 or the DCCAprocedure 1155 performed in the example 1100 or 1150, the length of thefirst signal described with reference to FIG. 11C may be shorter thanthe length of the first signal described with reference to FIGS. 11Aand/or 11B.

In some examples, information as discussed above may be transmitted aspart of the first signal 1135 (e.g., as part of the unit training signal1135-c). In some examples, the first signal 1135 (e.g., the unittraining signal 1135-c) may be usable for AGC by a UE.

In some examples, the first signal 1135 may be associated with acontention priority (e.g., a priority with which the DCCA procedure 1175is performed), and the first signal 1135 may be transmitted during aportion of the first OFDM symbol period 1110 based at least in part onthe contention priority. For example, a base station having a class oftraffic or transmission with a higher priority may be configured tocontend for access to a radio frequency spectrum band at an earlierportion of the first OFDM symbol period 1110 than a base station havinga class of traffic or transmission with a lower priority. The first OFDMsymbol period 1110 may provide relatively more or relatively fewer slotsfor performing DCCA procedures, and in some examples, slots forperforming DCCA procedures may be provided over more than one OFDMsymbol period. More slots for performing DCCA procedures translates tomore control over the contention priorities of different base stations.

In some examples of the wireless communication system 100 and/or 200described with reference to FIGS. 1 and/or 2, transmissions between abase station and a UE may be made in LBT radio frames of different size,such as, in LBT radio frames having durations of two milliseconds, fivemilliseconds, and/or ten milliseconds. In some examples, it may beuseful to make one or more overhead channel transmissions at a time ortimes and/or at a frequency location and/or locations, regardless of theLBT radio frame duration. For example, it may be desirable to make oneor more overhead channel transmissions during one or more subframesregardless of a change in an LBT radio frame in which an LBT procedureoccurs. The overhead channels may include a CRS, eCRS, CSI-RS,synchronization signal, and/or a system information block (SIB)broadcast channel.

FIG. 12 shows an example 1200 of how a first signal may be transmittedwhile operating in an LBT-LBE mode of operation in a radio frequencyspectrum band, to align a starting point of a second signal with areference boundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure. Moreparticularly, FIG. 12 shows an LBT-LBE radio frame 1205 having aduration of 2 ms. The LBT-LBE radio frame 1205 may include a firstLTE/LTE-A subframe 1210 and a second LTE/LTE-A subframe 1215, eachhaving a duration of 1 ms. Each of the first LTE/LTE-A subframe 1210 andthe second LTE/LTE-A subframe 1215 may include a plurality of OFDMsymbol periods 1220 (e.g., 14 OFDM symbol periods) bounded by aplurality of OFDM symbol period boundaries 1225.

In some examples, a base station may transmit a synchronization oralignment signal during a first part of the first LBT-LBE radio frame1205 (e.g., at or near the beginning of the first LBT-LBE radio frame1205). The synchronization or alignment signal may be transmitted, forexample, because the timing of the start of the LBT-LBE radio frame 1205can vary based on the timing of the conclusion of a successful extendedCCA procedure (e.g., the timing of the conclusion of the successfulextended CCA procedure can vary with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of an LBT-FBE framestructure over the radio frequency spectrum band, with reference to thetiming of a discovery signal (e.g., a CET) transmitted over the radiofrequency spectrum band, and/or with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of a transmission overa licensed radio frequency spectrum band (e.g., an OFDM symbol boundary,slot boundary, and/or subframe boundary of a transmission from a primaryserving cell over the licensed radio frequency spectrum band)), and/orbecause OFDM symbol level synchronization may be desirable among thedownlink transmissions of a base station or eNB.

In some examples, the synchronization or alignment signal may include avariable length training sequence 1230 (e.g., a fractional CUBS having aduration less than a duration of an OFDM symbol period 1220) but nofixed length training sequence 1235. In other examples, thesynchronization or alignment signal may include a variable lengthtraining sequence 1230 and at least one fixed length training sequence1235 (e.g., at least one CUBS, each spanning an OFDM symbol period). Inother examples, the synchronization or alignment signal may include afixed length training sequence 1235 but no variable length trainingsequence 1230. The variable length training sequence 1230 and/or fixedlength training sequence 1235 (which may individually or collectivelyconstitute a first signal) may in some examples be used to align adownlink transmission with a boundary 1230 of an OFDM symbol period1220.

By way of example, FIG. 12 shows the first LTE/LTE-A subframe 1210starting with an OFF time 1240, followed by a variable length trainingsequence 1230, a fixed length training sequence 1235, and a downlinktransmission 1245. In some examples, the OFF time 1240 may have aduration of 100 microseconds (μsec), determined, for example, by aminimum OFF time of 100 μsec for LBT-FBE transmissions and a maximum OFFtime of 100 μsec (5×20 μsec) for LBT-LBE transmissions.

FIG. 13 shows an example 1300 of how a first signal may be transmittedwhile operating in an LBT-LBE mode of operation in a radio frequencyspectrum band, to align a starting point of a second signal with areference boundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure. Moreparticularly, FIG. 13 shows an LBT-LBE radio frame 1305 having aduration of 4 ms. The LBT-LBE radio frame 1305 may include a firstLTE/LTE-A subframe 1310, a second LTE/LTE-A subframe 1315, a thirdLTE/LTE-A subframe 1320, and a fourth LTE/LTE-A subframe 1325, eachhaving a duration of 1 ms. Each of the first LTE/LTE-A subframe 1310,the second LTE/LTE-A subframe 1315, the third LTE/LTE-A subframe 1320,and the fourth LTE/LTE-A subframe 1325 may include a plurality of OFDMsymbol periods 1330 (e.g., 14 OFDM symbol periods) bounded by aplurality of OFDM symbol period boundaries 1335.

In some examples, a base station may transmit a synchronization oralignment signal during a first part of the first LBT-LBE radio frame1305 (e.g., at or near the beginning of the first LBT-LBE radio frame1305). The synchronization or alignment signal may be transmitted, forexample, because the timing of the start of the LBT-LBE radio frame 1305can vary based on the timing of the conclusion of a successful extendedCCA procedure (e.g., the timing of the conclusion of the successfulextended CCA procedure can vary with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of an LBT-FBE framestructure over the radio frequency spectrum band, with reference to thetiming of a discovery signal (e.g., a CET) transmitted over the radiofrequency spectrum band, and/or with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of a transmission overa licensed radio frequency spectrum band (e.g., an OFDM symbol boundary,slot boundary, and/or subframe boundary of a transmission from a primaryserving cell over the licensed radio frequency spectrum band)), and/orbecause OFDM symbol level synchronization may be desirable among thedownlink transmissions of a base station or eNB.

In some examples, the synchronization or alignment signal may include avariable length training sequence 1340 (e.g., a fractional CUBS having aduration less than a duration of an OFDM symbol period 1330) but nofixed length training sequence 1345. In other examples, thesynchronization or alignment signal may include a variable lengthtraining sequence 1340 and at least one fixed length training sequence1345 (e.g., at least one CUBS, each spanning an OFDM symbol period). Inother examples, the synchronization or alignment signal may include afixed length training sequence 1345 but no variable length trainingsequence 1340. The variable length training sequence 1340 and/or fixedlength training sequence 1345 (which may individually or collectivelyconstitute a first signal) may in some examples be used to align adownlink transmission with a boundary 1335 of an OFDM symbol period1330.

By way of example, FIG. 13 shows the first LTE/LTE-A subframe 1310starting with an OFF time 1350, followed by a variable length trainingsequence 1340, a fixed length training sequence 1345, and a downlinktransmission 1355. In some examples, the OFF time 1350 may have aduration of 200 microseconds (μsec), determined, for example, by aminimum OFF time of 200 μsec for LBT-FBE transmissions and a maximum OFFtime of 200 μsec (10×20 μsec) for LBT-LBE transmissions.

FIG. 14 shows an example 1400 of how a first signal may be transmittedwhile operating in an LBT-LBE mode of operation in a radio frequencyspectrum band, to align a starting point of a second signal with areference boundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure. Moreparticularly, FIG. 14 shows an LBT-LBE radio frame 1405 having aduration of 10 ms. The LBT-LBE radio frame 1405 may include tenLTE/LTE-A subframes, including a first LTE/LTE-A subframe 1410, a secondLTE/LTE-A subframe 1415, and a tenth LTE/LTE-A subframe 1420, eachhaving a duration of 1 ms. Each of the LTE/LTE-A subframes (includingthe first LTE/LTE-A subframe 1410, the second LTE/LTE-A subframe 1415,and the tenth LTE/LTE-A subframe 1420 may include a plurality of OFDMsymbol periods 1425 (e.g., 14 OFDM symbol periods) bounded by aplurality of OFDM symbol period boundaries 1430.

In some examples, a base station may transmit a synchronization oralignment signal during a first part of the first LBT-LBE radio frame1405 (e.g., at or near the beginning of the first LBT-LBE radio frame1405). The synchronization or alignment signal may be transmitted, forexample, because the timing of the start of the LBT-LBE radio frame 1405can vary based on the timing of the conclusion of a successful extendedCCA procedure (e.g., the timing of the conclusion of the successfulextended CCA procedure can vary with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of an LBT-FBE framestructure over the radio frequency spectrum band, with reference to thetiming of a discovery signal (e.g., a CET) transmitted over the radiofrequency spectrum band, and/or with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of a transmission overa licensed radio frequency spectrum band (e.g., an OFDM symbol boundary,slot boundary, and/or subframe boundary of a transmission from a primaryserving cell over the licensed radio frequency spectrum band)), and/orbecause OFDM symbol level synchronization may be desirable among thedownlink transmissions of a base station or eNB.

In some examples, the synchronization or alignment signal may include avariable length training sequence 1435 (e.g., a fractional CUBS having aduration less than a duration of an OFDM symbol period 1425) but nofixed length training sequence 1440. In other examples, thesynchronization or alignment signal may include a variable lengthtraining sequence 1435 and at least one fixed length training sequence1440 (e.g., at least one CUBS, each spanning an OFDM symbol period). Inother examples, the synchronization or alignment signal may include afixed length training sequence 1440 but no variable length trainingsequence 1435. The variable length training sequence 1435 and/or fixedlength training sequence 1440 (which may individually or collectivelyconstitute a first signal) may in some examples be used to align adownlink transmission with a boundary 1430 of an OFDM symbol period1425.

By way of example, FIG. 14 shows the first LTE/LTE-A subframe 1410starting with an OFF time 1445, followed by a variable length trainingsequence 1435, a fixed length training sequence 1440, and a downlinktransmission 1450. In some examples, the OFF time 1445 may have aduration of 500 microseconds (μsec), determined, for example, by aminimum OFF time of 500 μsec for LBT-FBE transmissions and a maximum OFFtime of 500 μsec (25×20 μsec) for LBT-LBE transmissions.

FIG. 15 shows an example 1500 of how a first signal may be transmittedwhile operating in an LBT-LBE mode of operation in a radio frequencyspectrum band, to align a starting point of a second signal with areference boundary associated with the radio frequency spectrum band, inaccordance with various aspects of the present disclosure. Moreparticularly, FIG. 15 shows an LBT-LBE radio frame 1505 having aduration of 10 ms. The LBT-LBE radio frame 1505 may include tenLTE/LTE-A subframes, including a first LTE/LTE-A subframe 1510, a secondLTE/LTE-A subframe 1515, and a tenth LTE/LTE-A subframe 1520, eachhaving a duration of 1 ms. Each of the LTE/LTE-A subframes (includingthe first LTE/LTE-A subframe 1510, the second LTE/LTE-A subframe 1515,and the tenth LTE/LTE-A subframe 1520 may include a plurality of OFDMsymbol periods 1525 (e.g., 14 OFDM symbol periods) bounded by aplurality of OFDM symbol period boundaries 1530.

In some examples, a base station may transmit a synchronization oralignment signal during a first part of the first LBT-LBE radio frame1505 (e.g., at or near the beginning of the first LBT-LBE radio frame1505). The synchronization or alignment signal may be transmitted, forexample, because the timing of the start of the LBT-LBE radio frame 1505can vary based on the timing of the conclusion of a successful extendedCCA procedure (e.g., the timing of the conclusion of the successfulextended CCA procedure can vary with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of an LBT-FBE framestructure over the radio frequency spectrum band, with reference to thetiming of a discovery signal (e.g., a CET) transmitted over the radiofrequency spectrum band, and/or with reference to an OFDM symbolboundary, slot boundary, and/or subframe boundary of a transmission overa licensed radio frequency spectrum band (e.g., an OFDM symbol boundary,slot boundary, and/or subframe boundary of a transmission from a primaryserving cell over the licensed radio frequency spectrum band)), and/orbecause OFDM symbol level synchronization may be desirable among thedownlink transmissions of a base station or eNB.

In some examples, the synchronization or alignment signal may include avariable length training sequence 1535 (e.g., a fractional CUBS having aduration less than a duration of an OFDM symbol period 1525) but nofixed length training sequence. In other examples, the synchronizationor alignment signal may include a variable length training sequence 1535and at least one fixed length training sequence 1540, 1545, 1550, 1555,1560, 1565, and/or 1570 (e.g., at least one CUBS, each spanning an OFDMsymbol period). In other examples, the synchronization or alignmentsignal may include a fixed length training sequence 1540, 1545, 1550,1555, 1560, 1565, and/or 1570 but no variable length training sequence1535. The variable length training sequence 1535 and/or fixed lengthtraining sequence 1540, 1545, 1550, 1555, 1560, 1565, and/or 1570 (whichmay individually or collectively constitute a first signal) may in someexamples be used to align a downlink transmission with a boundary 1530of an OFDM symbol period 1525, as well as a boundary 1575 of the secondLTE/LTE-A subframe 1515.

By way of example, FIG. 15 shows the first LTE/LTE-A subframe 1510starting with an OFF time 1580, followed by a variable length trainingsequence 1535, a plurality of fixed length training sequences 1540,1545, 1550, 1555, 1560, 1565, and 1570, and a downlink transmission1585. In some examples, the OFF time 1580 may have a duration of 500microseconds (μsec), determined, for example, by a minimum OFF time of500 μsec for LBT-FBE transmissions and a maximum OFF time of 500 μsec(25×20 μsec) for LBT-LBE transmissions.

FIG. 3 and FIGS. 12-15 illustrate LBT radio frames (e.g., LBT-FBE radioframes and/or LBT-LBE radio frames) having different durations (e.g., 2ms, 4 ms, or 10 ms). The duration of an LBT radio frame may have animpact on uplink transmissions to a secondary serving cell over a radiofrequency spectrum band. Uplink data transmissions are scheduled, andonly UEs having scheduled uplink data transmissions may perform a UCCAprocedure. In a time domain duplexing (TDD) frame configuration, a lastdownlink subframe before an uplink subframe may be truncated to providefor timing advance (TA) and performance of a UCCA procedure.

Scheduled uplink data transmissions (e.g., uplink subframes) may beadvertised in a downlink subframe. The advertisement of uplink datatransmissions helps to prevent neighboring base stations or eNBs fromgrabbing one or more channels of the radio frequency spectrum bandneeded for the scheduled uplink data transmissions and prevents blockingof reception on the uplink at the serving eNB.

In some examples, LBT radio frames may be transmitted to a UE from asecondary serving cell over a radio frequency spectrum band, and the LBTradio frames may have durations of 2 ms, with either all downlinksubframe or all uplink subframe configurations. In these examples,uplink grants for the uplink subframes may be transmitted in downlinksubframes of the secondary serving cell, with a UL grant delay of 2 msor less. In some examples, LBT radio frames may be transmitted to a UEfrom a secondary serving cell over a radio frequency spectrum band, andthe LBT radio frames may have durations of 4 ms or 5 ms, with either alldownlink subframe or all uplink subframe configurations. In theseexamples, uplink grants for the uplink subframes may be transmitted indownlink subframes of the secondary serving cell, with a UL grant delayas specified in Release 8 of the LTE/LTE-A specification. Alternatively,uplink grants for the uplink subframes may be transmitted in downlinksubframes of a primary serving cell, with a UL grant delay up to 1 mslonger or shorter than specified in Release 8 of the LTE/LTE-Aspecification. In some examples, LBT radio frames may be transmitted toa UE from a secondary serving cell over a radio frequency spectrum band,and the LBT radio frames may have durations of 10 ms, in accord with oneor more TDD configurations including both downlink subframes and uplinksubframes. In these examples, uplink grants for the uplink subframes maybe transmitted in downlink subframes of the secondary serving cell, witha UL grant delay that is the same or similar as that specified inRelease 8 of the LTE/LTE-A specification. Alternatively, uplink grantsfor the uplink subframes may be transmitted in downlink subframes of aprimary serving cell, with a UL grant delay that is the same or similaras that specified in Release 11 of the LTE/LTE-A specification.

FIG. 16 shows an example 1600 of how one or more overhead transmissionmay be made in a radio frequency spectrum band, in accordance withvarious aspects of the present disclosure. More particularly, FIG. 16shows a first subframe 1655 of a first frame period (e.g., a first LBTradio frame), and a first subframe 1660 of a second frame period (e.g.,a second LBT radio frame). Each of the first subframe 1655 and the firstsubframe 1660 may include a plurality of OFDM symbol periods.

Upon winning contention to access a radio frequency spectrum band duringthe first frame period, a transmitting apparatus may transmit a signalat a periodicity (e.g., a fixed periodicity). The signal may betransmitted at the periodicity during one or more subframes (e.g., thefirst subframe 1655) of the first frame period. When the transmittingapparatus transmits a plurality of different frame periods (e.g., tenmillisecond, five millisecond, and/or two millisecond frame periods),which the plurality of different frame periods include the second frameperiod, or when the transmitting apparatus selects the first frameperiod among a plurality of different frame periods including the secondframe period, the transmitting apparatus may transmit the signal at theperiodicity for each of the plurality of different frame periods. Thatis, the signal may be transmitted at the periodicity regardless of theframe in which the transmitting apparatus wins the contention, therebymaking processing of the signal transparent to a receiving apparatusregardless of a change in the frame in which the transmitting apparatuswins the contention to access the radio frequency spectrum. In someexamples, the signal may be transmitted in an overhead channel, and theoverhead channels may include a CRS, eCRS, CSI-RS, synchronizationsignal, and/or an SIB broadcast channel.

As shown, the signal may be transmitted in OFDM symbol periods 1610,1615, 1620, and/or 1625 of the first subframe 1655 of the first frameperiod. The signal may also or alternately be transmitted in OFDM symbolperiods 1630, 1635, 1640, and/or 1645 of the first subframe 1660 of thesecond frame period. The OFDM symbol periods 1610, 1615, 1620, and 1625may be aligned in time with respective ones of the OFDM symbol periods1630, 1635, 1640, and 1645, to enable transmission of the signal at afixed time or times. The signal may also be transmitted at a fixedfrequency location or locations in each of the OFDM symbol periods.

When a transmission of the signal is determined to collide with a timingof a contention procedure 1650, transmission of the signal may beprevented. For example, transmission of the signal in the OFDM symbolperiod 1630 of the first subframe 1660 may be determined to collide withthe timing of the contention procedure 1650, and thus, transmission ofthe signal during OFDM symbol period 1630 may be prevented.

FIG. 17 shows a block diagram 1700 of an apparatus 1705 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 1705 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, and/or an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2. The apparatus 1705 mayalso be a processor. The apparatus 1705 may include a receiver module1710, a wireless communication management module 1720, and/or atransmitter module 1730. Each of these components may be incommunication with each other.

The components of the apparatus 1705 may, individually or collectively,be implemented using one or more application-specific integratedcircuits (ASICs) adapted to perform some or all of the applicablefunctions in hardware. Alternatively, the functions may be performed byone or more other processing units (or cores), on one or more integratedcircuits. In other examples, other types of integrated circuits may beused (e.g., Structured/Platform ASICs, Field Programmable Gate Arrays(FPGAs), and other Semi-Custom ICs), which may be programmed in anymanner known in the art. The functions of each unit may also beimplemented, in whole or in part, with instructions embodied in amemory, formatted to be executed by one or more general orapplication-specific processors.

In some examples, the receiver module 1710 may include at least oneradio frequency (RF) receiver, such as at least one RF receiver operableto receive transmissions over a licensed radio frequency spectrum band(e.g., a radio frequency spectrum band for which apparatuses may contendfor access because the radio frequency spectrum band is licensed tomultiple users to share access to) and/or an unlicensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may need to contend for access because the radio frequencyspectrum band is available for unlicensed use, such as Wi-Fi use). Insome examples, the licensed radio frequency spectrum band and/or theunlicensed radio frequency spectrum band may be used for LTE/LTE-Acommunications, as described, for example, with reference to FIGS. 1and/or 2. The receiver module 1710 may be used to receive various typesof data and/or control signals (i.e., transmissions) over one or morecommunication links of a wireless communication system, such as one ormore communication links of the wireless communication system 100 and/or200 described with reference to FIGS. 1 and/or 2. The communicationlinks may be established over the licensed radio frequency spectrum bandand/or the unlicensed radio frequency spectrum band.

In some examples, the transmitter module 1730 may include at least oneRF transmitter, such as at least one RF transmitter operable to transmitover the licensed radio frequency spectrum band and/or the unlicensedradio frequency spectrum band. The transmitter module 1730 may be usedto transmit various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 1720 maybe used to manage one or more aspects of wireless communication for theapparatus 1705. In some examples, the wireless communication managementmodule 1720 may be used to transmit information (e.g., N bits ofinformation) over a channel in the radio frequency spectrum band. Forexample, the wireless communication management module 1720 may be usedto transmit information with a signal that indicates accessing (e.g.,the reserving of) a channel in the radio frequency spectrum band. Insome examples, the signal that indicates accessing the channel in theradio frequency spectrum band may include a CUBS such as the CUBS 445and/or 545 described with reference to FIGS. 4 and/or 5. In one example,the information may be transmitted as part of the signal that indicatesaccessing the channel in the radio frequency spectrum band. In anotherexample, the information may be transmitted as a separate signal alongwith the signal that indicates accessing the channel in the radiofrequency spectrum band. The transmitted information may aid a receivingapparatus in decoding a transmission that follows the information and/orenable the receiving apparatus to conserve power, etc.

In some examples, the wireless communication management module 1720 maybe used to transmit a signal when a successful contention procedure(e.g., a DCCA procedure or UCCA procedure) concludes before a referenceboundary associated with a radio frequency spectrum band (e.g., before aboundary of a next OFDM symbol period). The first signal may be used toalign a starting point of a second signal with the reference boundaryassociated with the radio frequency spectrum band. In some examples, thecommencement of the first signal may not coincide with a referenceboundary of the radio frequency spectrum band, and the length of thefirst signal may be variable due to variances in the timing between whena contention procedure is performed and when a reference boundary (e.g.,a boundary of a next OFDM symbol period) occurs.

In some examples, the wireless communication management module 1720 maybe used to make one or more overhead channel transmissions (e.g., eCRS,CSI-RS, synchronization signal, and/or an SIB broadcast channeltransmissions) at a time or times and/or at a frequency location and/orlocations, regardless of the duration (e.g., two milliseconds, fivemilliseconds, and/or ten milliseconds) of an LBT radio frame period. Forexample, the wireless communication management module 1720 may make oneor more overhead channel transmissions during one or more subframesregardless of the duration of an LBT radio frame in which the subframesoccur.

FIG. 18 shows a block diagram 1800 of an apparatus 1805 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 1805 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 described with reference to FIG. 17. Theapparatus 1805 may also be a processor. The apparatus 1805 may include areceiver module 1810, a wireless communication management module 1820,and/or a transmitter module 1830. Each of these components may be incommunication with each other.

The components of the apparatus 1805 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1810 may be an example of one ormore aspects of the receiver module 1710 described with reference toFIG. 17. In some examples, the receiver module 1810 may include at leastone radio frequency (RF) receiver, such as at least one RF receiveroperable to receive transmissions over a licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 1810 may be used toreceive various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 1830 may be an example of oneor more aspects of the transmitter module 1730 described with referenceto FIG. 17. In some examples, the transmitter module 1830 may include atleast one RF transmitter, such as at least one RF transmitter operableto transmit over the licensed radio frequency spectrum band and/or theunlicensed radio frequency spectrum band. The transmitter module 1830may be used to transmit various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 1820 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 described with reference to FIG. 17. The wirelesscommunication management module 1820 may include a channel accessindication module 1835 and/or an information transmission module 1840.Each of these components may be in communication with each other.

In some examples, the channel access indication module 1835 may be usedto transmit a first signal to indicate accessing (e.g., a reserving of)a first channel in the radio frequency spectrum band.

In some examples, the channel access indication module 1835 may transmitthe first signal using a plurality of interleaved resource blocks.Transmitting the first signal in this manner may enable the first signalto occupy at least a certain percentage of the available frequencybandwidth in the radio frequency spectrum band and/or satisfy one ormore regulatory requirements (e.g., a requirement that the first signaloccupy at least 80% of the available frequency bandwidth).

In some examples, the information transmission module 1840 may be usedto transmit information with the first signal in the radio frequencyspectrum band. The transmitted information may include various types ofinformation. In some examples, the information may include a cell ID, aPLMN ID, or a combination thereof. In some examples, the information mayindicate a frame structure for transmission in the radio frequencyspectrum band (e.g., the LBT radio frame duration). In some examples,the information may indicate a number of subframes and/or symbols thatwill be used for transmission in a frame structure in the radiofrequency spectrum band (e.g., five subframes are used for transmissionin a ten millisecond frame duration that includes ten subframes). Anindication of a number of subframes and/or symbols that will be used fortransmission in a frame structure in the radio frequency spectrum bandmay enable a receiving apparatus, such as a UE, to enter a low powerstate at an earlier time (e.g., immediately after receiving thetransmitted subframes), thereby conserving power. In some examples, theinformation may indicate an uplink configuration and/or a downlinkconfiguration for transmission in the radio frequency spectrum band(e.g., an uplink configuration and/or a downlink configuration of aframe structure in the radio frequency spectrum band). An indication ofan uplink configuration and/or a downlink configuration for transmissionin the radio frequency spectrum band may improve the performance ofeIMTA functionality. In some examples, the information may indicatewhether a maximum number of subframes, of a frame, are used fortransmission in the radio frequency spectrum band (e.g., a single bitmay be used to indicate whether a maximum number of subframes are usedfor transmission in a frame structure of the radio frequency spectrumband, or whether fewer than the maximum number of subframes are used fortransmission in the frame structure of the radio frequency spectrumband). In some examples, the information may indicate a number ofantennas to use for receiving a transmission carried on a componentcarrier in the radio frequency spectrum band (e.g., a number of antennasto receive transmission of the component carrier during a framestructure of the radio frequency spectrum band, as described, forexample, with reference to FIGS. 9 and/or 10). The information may alsoor alternatively include any combination of the above types ofinformation and/or other types of information, including other types ofsystem information.

FIG. 19 shows a block diagram 1900 of an apparatus 1905 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 1905 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 and/or 1805 described with reference toFIGS. 17 and/or 18. The apparatus 1905 may also be a processor. Theapparatus 1905 may include a receiver module 1910, a wirelesscommunication management module 1920, and/or a transmitter module 1930.Each of these components may be in communication with each other.

The components of the apparatus 1905 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1910 may be an example of one ormore aspects of the receiver module 1710 and/or 1810 described withreference to FIGS. 17 and/or 18. In some examples, the receiver module1910 may include at least one RF receiver, such as at least one RFreceiver operable to receive transmissions over licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 1910 may in somecases include separate receivers for the licensed radio frequencyspectrum band and the unlicensed radio frequency spectrum band. Theseparate receivers may, in some examples, take the form of a licensed RFspectrum band LTE/LTE-A receiver module 1912 for communicating over thelicensed radio frequency spectrum band, and an unlicensed RF spectrumband LTE/LTE-A receiver module 1914 for communicating over theunlicensed radio frequency spectrum band. The receiver module 1910,including the licensed RF spectrum band LTE/LTE-A receiver module 1912and/or the unlicensed RF spectrum band LTE/LTE-A receiver module 1914,may be used to receive various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 1930 may be an example of oneor more aspects of the transmitter module 1730 and/or 1830 describedwith reference to FIGS. 17 and/or 18. In some examples, the transmittermodule 1930 may include at least one RF transmitter, such as at leastone RF transmitter operable to transmit over the licensed radiofrequency spectrum band and/or the unlicensed radio frequency spectrumband. The transmitter module 1930 may in some cases include separatetransmitters for the licensed radio frequency spectrum band and theunlicensed radio frequency spectrum band. The separate transmitters may,in some examples, take the form of a licensed RF spectrum band LTE/LTE-Atransmitter module 1932 for communicating over the licensed radiofrequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-Atransmitter module 1934 for communicating over the unlicensed radiofrequency spectrum band. The transmitter module 1930, including thelicensed RF spectrum band LTE/LTE-A transmitter module 1932 and/or theunlicensed RF spectrum band LTE/LTE-A transmitter module 1934, may beused to transmit various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 1920 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 and/or 1820 described with reference to FIGS. 17and/or 18. The wireless communication management module 1920 may includea contention management module 1935, a channel access indication module1940, an information transmission module 1945, an antenna selectionmodule 1960, an MCS adjustment module 1965, and/or a data transmissionmodule 1970. Each of these components may be in communication with eachother.

In some examples, the contention management module 1935 may be used toperform a contention procedure to contend for access to one or morechannels of the radio frequency spectrum band for a period of time(e.g., for a frame period of the radio frequency spectrum band).

In some examples, the channel access indication module 1940 may be anexample of one or more aspects of the channel access indication module1835 described with reference to FIG. 18. In some examples, the channelaccess indication module 1940 may be used to transmit a first signal toindicate accessing (e.g., a reserving of) a first channel in the radiofrequency spectrum band. In some examples, the first signal may betransmitted following a successful contention for access to the firstchannel in the radio frequency spectrum band.

In some examples, the channel access indication module 1940 may transmitthe first signal using a plurality of interleaved resource blocks.Transmitting the first signal in this manner may enable the first signalto occupy at least a certain percentage of the available frequencybandwidth in the radio frequency spectrum band and satisfy one or moreregulatory requirements (e.g., a requirement that the first signaloccupy at least 80% of the available frequency bandwidth).

In some examples, the information transmission module 1945 may be anexample of one or more aspects of the information transmission module1840 described with reference to FIG. 18. In some examples, theinformation transmission module 1945 may be used to transmit informationwith the first signal in the radio frequency spectrum band. Thetransmitted information may include various types of information. Insome examples, the information may include a cell ID, a PLMN ID, or acombination thereof. In some examples, the information may indicate aframe structure for transmission in the radio frequency spectrum band(e.g., the LBT radio frame duration). In some examples, the informationmay indicate a number of subframes and/or symbols that will be used fortransmission in a frame structure in the radio frequency spectrum band(e.g., five subframes are used for transmission in a ten millisecondframe duration that includes ten subframes). An indication of a numberof subframes and/or symbols that will be used for transmission in aframe structure in the radio frequency spectrum band may enable areceiving apparatus, such as a UE, to enter a low power state at anearlier time (e.g., immediately after receiving the transmittedsubframes), thereby conserving power. In some examples, the informationmay indicate an uplink configuration and/or a downlink configuration fortransmission in the radio frequency spectrum band (e.g., an uplinkconfiguration and/or a downlink configuration of a frame structure inthe radio frequency spectrum band). An indication of an uplinkconfiguration and/or a downlink configuration for transmission in anunlicensed radio frequency spectrum band may improve the performance ofeIMTA functionality. In some examples, the information may indicatewhether a maximum number of subframes, of a frame, are used fortransmission in a radio frequency spectrum band (e.g., a single bit maybe used to indicate whether a maximum number of subframes are used fortransmission in a frame structure of the radio frequency spectrum band,or whether fewer than the maximum number of subframes are used fortransmission in the frame structure of the radio frequency spectrumband). In some examples, the information may indicate a number ofantennas to use for receiving a transmission carried on a componentcarrier in the radio frequency spectrum band (e.g., a number of antennasto receive transmission of the component carrier during a framestructure of the radio frequency spectrum band, as described, forexample, with reference to FIGS. 9 and/or 11). The information may alsoor alternatively include any combination of the above types ofinformation and/or other types of information, including other types ofsystem information.

In some examples, the information transmission module 1945 may transmitinformation with the first signal by causing the channel accessindication module 1940 to transmit the information as part of the firstsignal. For example, the information transmission module 1945 mayinclude a sequence selection module 1950 that may be used to select orgenerate a sequence that is a function of the information to betransmitted. For example, the sequence may be a function of a cell ID, aPLMN ID, or a combination thereof. The sequence may also oralternatively be a function of any one or combination of the types ofinformation referenced herein. In these examples, the informationtransmission module 1945 may cause the channel access indication module1940 to generate the first signal based at least in part on the selectedor generated sequence.

In other examples in which the information transmission module 1945 maytransmit information with the first signal by transmitting theinformation as part of the first signal, the information transmissionmodule 1945 may include a phase selection module 1955. The phaseselection module 1955 may be used to select a first phase from among aplurality of phases for transmission of the first signal. Differentphases of the plurality of phases may correspond to differentinformation, and the first phase may correspond to information to betransmitted. In these examples, the information transmission module 1945may cause the channel access indication module 1940 to transmit thefirst signal at the first phase.

In some examples, the information transmission module 1945 may transmitinformation with the first signal by transmitting the information in asecond signal along with the first signal. The second signal may beseparate from the first signal.

In some examples, the channel access indication module 1940 may transmitthe first signal and the information during a single OFDM symbol periodof the radio frequency spectrum band. In some examples, the channelaccess indication module 1940 may transmit the first signal during afirst OFDM symbol period of the radio frequency spectrum band and asecond OFDM symbol period of the radio frequency spectrum band, and theinformation transmission module 1945 may transmit information with thefirst signal by transmitting the information during the second OFDMsymbol period of the radio frequency spectrum band. In some examples,the first OFDM symbol period of the radio frequency spectrum band andthe second OFDM symbol period of the radio frequency spectrum band maybe adjacent OFDM symbol periods.

In some examples, the information transmission module 1945 may transmitinformation with the first signal in the radio frequency spectrum bandby transmitting a second signal carrying the information in the radiofrequency spectrum band. When the first signal is transmitted during afirst OFDM symbol period of the radio frequency spectrum band and asecond OFDM symbol period of the radio frequency spectrum band, theinformation transmission module 1945 may in some examples transmit thesecond signal during the second OFDM symbol period of the radiofrequency spectrum band. In these examples, the first signal may provideAGC information and/or a phase reference for the second signal.

When the information transmission module 1945 transmits information withthe first signal in the radio frequency spectrum band by transmitting asecond signal carrying the information in the radio frequency spectrumband, the first signal may be transmitted using a first plurality ofinterleaved resource blocks and/or the second signal may be transmittedusing a second plurality of interleaved resource blocks. Transmittingthe first signal and/or the second signal in this manner may enable thefirst signal and/or the second signal to occupy at least a certainpercentage of the available frequency bandwidth in the radio frequencyspectrum band and/or satisfy one or more regulatory requirements (e.g.,a requirement that the first signal and/or second signal occupy at least80% of the available frequency bandwidth).

In some examples, the antenna selection module 1960 may be used todetermine a number of antennas to use for receiving a transmissioncarried on a component carrier in the radio frequency spectrum band. Insome examples, the antenna selection module 1960 may be used todetermine a number of antennas to use for receiving a transmissioncarried on the component carrier in the radio frequency spectrum bandbased at least in part on an uplink configuration or a downlinkconfiguration associated with the component carrier (e.g., an uplinkconfiguration or a downlink configuration associated with a frame and/ora subframe of the component carrier). In the same or other examples, theantenna selection module 1960 may determine the number of antennas touse for receiving a transmission carried on the component carrier in theradio frequency spectrum band based at least in part on a contentionprocedure associated with each of a plurality of component carriers usedto serve a UE (e.g., based at least in part on a success or failure ofthe contention procedure performed for each of the plurality ofcomponent carriers).

In some examples, the antenna selection module 1960 may select thenumber of antennas to use for receiving a transmission carried on thecomponent carrier in the radio frequency spectrum band for each subframeof a frame of the component carrier. In some examples, the antennaselection module 1960 may select the number of antennas to use forreceiving a transmission carried on the component carrier in the radiofrequency spectrum band for each frame of the component carrier.

In some examples, the MCS adjustment module 1965 may be used to adjustan MCS for a data transmission over the component carrier in the radiofrequency spectrum band. The MCS may be adjusted based at least in parton the number of antennas to use to receive the component carrier in theradio frequency spectrum band. The wireless communication managementmodule 1920 may also include a module for adjusting a precoding matrixand/or a rank for a data transmission.

In some examples, the data transmission module 1970 may be used totransmit a data transmission over a component carrier in the radiofrequency spectrum band. In some examples, the data transmission may betransmitted in accordance with an adjusted precoding matrix, rank,and/or MCS.

FIG. 20 shows a block diagram 2000 of an apparatus 2005 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 2005 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 described with reference to FIG. 17. Theapparatus 2005 may also be a processor. The apparatus 2005 may include areceiver module 2010, a wireless communication management module 2020,and/or a transmitter module 2030. Each of these components may be incommunication with each other.

The components of the apparatus 2005 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2010 may be an example of one ormore aspects of the receiver module 1710 described with reference toFIG. 17. In some examples, the receiver module 2010 may include at leastone radio frequency (RF) receiver, such as at least one RF receiveroperable to receive transmissions over a licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 2010 may be used toreceive various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 2030 may be an example of oneor more aspects of the transmitter module 1730 described with referenceto FIG. 17. In some examples, the transmitter module 2030 may include atleast one RF transmitter, such as at least one RF transmitter operableto transmit over the licensed radio frequency spectrum band and/or theunlicensed radio frequency spectrum band. The transmitter module 2030may be used to transmit various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 2020 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 described with reference to FIG. 17. The wirelesscommunication management module 2020 may include a contention managementmodule 2035 and/or an alignment signal transmission module 2040. Each ofthese components may be in communication with each other.

In some examples, the contention management module 2035 may be used toperform a contention procedure to contend for access to one or morechannels of the radio frequency spectrum band for a period of time(e.g., for a frame period of the radio frequency spectrum band).

In some examples, and after winning contention to access the radiofrequency spectrum band, the alignment signal transmission module 2040may be used to transmit a first signal to align a starting point of asecond signal with a reference boundary associated with the radiofrequency spectrum band. In some examples, the first signal may betransmitted before the second signal.

In some examples of the apparatus 2005, the first signal may include avariable length training sequence. The variable length training sequencemay, in some examples, include one or more transmission units of fixedduration. In other examples of the apparatus 2005, the first signal mayinclude a variable length training sequence and at least one fixedlength training sequence.

In some examples of the apparatus 2005, the second signal may include asignal indicating the winning contention to access the radio frequencyspectrum band (e.g., a CUBS). In other examples of the apparatus 2005(e.g., examples in which the apparatus 2005 is operating in an LBT-LBEmode of operation in radio frequency spectrum band), the second signalmay include a data transmission.

In examples of the apparatus 2005, the reference boundary may include aboundary of an OFDM symbol period. In these examples, the contentionprocedure performed by the contention management module 2035 may beperformed in accordance with a contention priority during the OFDMsymbol period. The contention priority may determine when the apparatus2005 performs a contention procedure within the OFDM symbol periodassociated with the radio frequency spectrum band. Thus, the contentionpriority may provide to the apparatus 2005, when the apparatus 2005performs a contention procedure earlier in time than another apparatus,a preference for winning the contention procedure over the otherapparatus. In some examples of the apparatus 2005, the first signal maybe associated with the contention priority of the apparatus 2005, suchthat the first signal is transmitted during a portion of the OFDM symbolperiod based at least in part on the contention priority. Thus, forexample, the first signal may be transmitted over a greater portion ofthe OFDM symbol period when the first signal is associated with acontention priority that allows the apparatus 2005 to perform acontention procedure earlier within the OFDM symbol period. Similarly,and by way of further example, the first signal may be transmitted overa smaller portion of the OFDM symbol period when the first signal isassociated with a contention priority that allows the apparatus 2005 toperform a contention procedure later within the OFDM symbol period.

In some examples, the alignment signal transmission module 2040 maytransmit information as part of the first signal. The information mayinclude, for example, AGC information and/or a phase reference for thesecond signal.

In some examples, the alignment signal transmission module 2040 maytransmit the first signal using a plurality of interleaved resourceblocks. Transmitting the first signal in this manner may enable thefirst signal to occupy at least a certain percentage of the availablefrequency bandwidth in the radio frequency spectrum band and/or satisfyone or more regulatory requirements (e.g., a requirement that the firstsignal occupy at least 80% of the available frequency bandwidth).

FIG. 21 shows a block diagram 2100 of an apparatus 2105 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 2105 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 and/or 2005 described with reference toFIGS. 17 and/or 20. The apparatus 2105 may also be a processor. Theapparatus 2105 may include a receiver module 2110, a wirelesscommunication management module 2120, and/or a transmitter module 2130.Each of these components may be in communication with each other.

The components of the apparatus 2105 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2110 may be an example of one ormore aspects of the receiver module 1710 and/or 2010 described withreference to FIGS. 17 and/or 20. In some examples, the receiver module2110 may include at least one RF receiver, such as at least one RFreceiver operable to receive transmissions over licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 2110 may in somecases include separate receivers for the licensed radio frequencyspectrum band and the unlicensed radio frequency spectrum band. Theseparate receivers may, in some examples, take the form of a licensed RFspectrum band LTE/LTE-A receiver module 2112 for communicating over thelicensed radio frequency spectrum band, and an unlicensed RF spectrumband LTE/LTE-A receiver module 2114 for communicating over theunlicensed radio frequency spectrum band. The receiver module 2110,including the licensed RF spectrum band LTE/LTE-A receiver module 2112and/or the unlicensed RF spectrum band LTE/LTE-A receiver module 2114,may be used to receive various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 2130 may be an example of oneor more aspects of the transmitter module 1730 and/or 2030 describedwith reference to FIGS. 17 and/or 20. In some examples, the transmittermodule 2130 may include at least one RF transmitter, such as at leastone RF transmitter operable to transmit over the licensed radiofrequency spectrum band and/or the unlicensed radio frequency spectrumband. The transmitter module 2130 may in some cases include separatetransmitters for the licensed radio frequency spectrum band and theunlicensed radio frequency spectrum band. The separate transmitters may,in some examples, take the form of a licensed RF spectrum band LTE/LTE-Atransmitter module 2132 for communicating over the licensed radiofrequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-Atransmitter module 2134 for communicating over the unlicensed radiofrequency spectrum band. The transmitter module 2130, including thelicensed RF spectrum band LTE/LTE-A transmitter module 2132 and/or theunlicensed RF spectrum band LTE/LTE-A transmitter module 2134, may beused to transmit various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 2120 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 and/or 2020 described with reference to FIGS. 17and/or 20. The wireless communication management module 2120 may includea timing information access module 2135, a contention management module2140, a reference boundary determination module 2145, and/or analignment signal transmission module 2150. Each of these components maybe in communication with each other.

In some examples, the timing information access module 2135 may be usedto access timing information. The timing information may include, forexample, a timing of one or more reference boundaries associated withthe radio frequency spectrum band.

In some examples, the contention management module 2140 may be anexample of one or more aspects of the contention management module 2035described with reference to FIG. 20. In some examples, the contentionmanagement module 2140 may be used to perform a contention procedure tocontend for access to one or more channels of the radio frequencyspectrum band for a period of time (e.g., for a frame period of theradio frequency spectrum band).

In some examples, the reference boundary determination module 2145 maybe used to determine a reference boundary (e.g., a reference boundaryoccurring after the winning contention to access the radio frequencyspectrum band) associated with the radio frequency spectrum band, basedat least in part on the timing information and the winning contention toaccess the radio frequency spectrum band.

In some examples, the alignment signal transmission module 2150 may bean example of one or more aspects of the alignment signal transmissionmodule 2040 described with reference to FIG. 20. In some examples, thealignment signal transmission module 2150 may be used to transmit afirst signal to align a starting point of a second signal with thedetermined reference boundary associated with the radio frequencyspectrum band. In some examples, the first signal may be transmittedbefore the second signal.

In some examples of the apparatus 2105, the first signal may include avariable length training sequence. The variable length training sequencemay, in some examples, include one or more transmission units of fixedduration. In other examples of the apparatus 2105, the first signal mayinclude a variable length training sequence and at least one fixedlength training sequence.

In some examples of the apparatus 2105, the second signal may include asignal indicating the winning contention to access the radio frequencyspectrum band (e.g., a CUBS). In other examples of the apparatus 2105(e.g., examples in which the apparatus 2105 is operating in an LBT-LBEmode of operation in radio frequency spectrum band), the second signalmay include a data transmission.

In examples of the apparatus 2105, the reference boundary may include aboundary of an OFDM symbol period. In these examples, the contentionprocedure performed by the contention management module 2140 may beperformed in accordance with a contention priority during the OFDMsymbol period. The contention priority may determine when the apparatus2105 performs a contention procedure within the OFDM symbol periodassociated with the radio frequency spectrum band. Thus, the contentionpriority may provide to the apparatus 2105, when the apparatus 2105performs a contention procedure earlier in time than another apparatus,a preference for winning the contention procedure over the otherapparatus. In some examples of the apparatus 2105, the first signal maybe associated with the contention priority of the apparatus 2105, suchthat the first signal is transmitted during a portion of the OFDM symbolperiod based at least in part on the contention priority. Thus, forexample, the first signal may be transmitted over a greater portion ofthe OFDM symbol period when the first signal is associated with acontention priority that allows the apparatus 2105 to perform acontention procedure earlier within the OFDM symbol period. Similarly,and by way of further example, the first signal may be transmitted overa smaller portion of the OFDM symbol period when the first signal isassociated with a contention priority that allows the apparatus 2105 toperform a contention procedure later within the OFDM symbol period.

In some examples, the reference boundary may include a boundary of aslot of a frame associated with the radio frequency spectrum band and/ora boundary of a subframe of a frame associated with the radio frequencyspectrum band.

In some examples, the alignment signal transmission module 2150 maytransmit information as part of the first signal. The information mayinclude, for example, AGC information and/or a phase reference for thesecond signal.

In some examples, the alignment signal transmission module 2150 maytransmit the first signal using a plurality of interleaved resourceblocks. Transmitting the first signal in this manner may enable thefirst signal to occupy at least a certain percentage of the availablefrequency bandwidth in the radio frequency spectrum band and/or satisfyone or more regulatory requirements (e.g., a requirement that the firstsignal occupy at least 80% of the available frequency bandwidth).

FIG. 22 shows a block diagram 2200 of an apparatus 2205 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 2205 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 and/or 2005 described with reference toFIGS. 17 and/or 20. The apparatus 2205 may also be a processor. Theapparatus 2205 may include a receiver module 2210, a wirelesscommunication management module 2220, and/or a transmitter module 2230.Each of these components may be in communication with each other.

The components of the apparatus 2205 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2210 may be an example of one ormore aspects of the receiver module 1710 and/or 2010 described withreference to FIGS. 17 and/or 20. In some examples, the receiver module2210 may include at least one RF receiver, such as at least one RFreceiver operable to receive transmissions over licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 2210 may in somecases include separate receivers for the licensed radio frequencyspectrum band and the unlicensed radio frequency spectrum band. Theseparate receivers may, in some examples, take the form of a licensed RFspectrum band LTE/LTE-A receiver module 2212 for communicating over thelicensed radio frequency spectrum band, and an unlicensed RF spectrumband LTE/LTE-A receiver module 2214 for communicating over theunlicensed radio frequency spectrum band. The receiver module 2210,including the licensed RF spectrum band LTE/LTE-A receiver module 2212and/or the unlicensed RF spectrum band LTE/LTE-A receiver module 2214,may be used to receive various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 2230 may be an example of oneor more aspects of the transmitter module 1730 and/or 2030 describedwith reference to FIGS. 17 and/or 20. In some examples, the transmittermodule 2230 may include at least one RF transmitter, such as at leastone RF transmitter operable to transmit over the licensed radiofrequency spectrum band and/or the unlicensed radio frequency spectrumband. The transmitter module 2230 may in some cases include separatetransmitters for the licensed radio frequency spectrum band and theunlicensed radio frequency spectrum band. The separate transmitters may,in some examples, take the form of a licensed RF spectrum band LTE/LTE-Atransmitter module 2232 for communicating over the licensed radiofrequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-Atransmitter module 2234 for communicating over the unlicensed radiofrequency spectrum band. The transmitter module 2230, including thelicensed RF spectrum band LTE/LTE-A transmitter module 2232 and/or theunlicensed RF spectrum band LTE/LTE-A transmitter module 2234, may beused to transmit various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 2220 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 and/or 2020 described with reference to FIGS. 17and/or 20. The wireless communication management module 2220 may includea contention management module 2235, a reference boundary determinationmodule 2250, an alignment signal transmission module 2255, and/or alocation information transmission module 2260. Each of these componentsmay be in communication with each other.

In some examples, the contention management module 2235 may be anexample of one or more aspects of the contention management module 2035described with reference to FIG. 20. In some examples, the contentionmanagement module 2235 may be used to perform a contention procedure tocontend for access to one or more channels of the radio frequencyspectrum band for a period of time (e.g., for a frame period of theradio frequency spectrum band). In some examples, the contentionmanagement module 2235 may include an LBT-LBE contention module 2240and/or an LBT-FBE contention module 2245. The LBT-LBE contention module2240 may be used to perform a contention procedure (e.g., an extendedCCA procedure) when the apparatus 2205 is operated in an LBT-LBE mode ofoperation over the radio frequency spectrum band. The LBT-FBE contentionmodule 2245 may be used to perform a contention procedure (e.g., a CCAprocedure) when the apparatus 2205 is operated in an LBT-FBE mode ofoperation over the radio frequency spectrum band. In some examples, thecontention management module 2235 may determine which of the LBT-LBEcontention module 2240 and the LBT-FBE contention module 2245 to usebased, for example, on a historical success of winning contention toaccess the radio frequency spectrum band using the LBT-FBE contentionmodule 2245.

In some examples, the reference boundary determination module 2250 maybe used to determine a reference boundary (e.g., a reference boundaryoccurring after the winning contention to access the radio frequencyspectrum band) associated with the radio frequency spectrum band, basedat least in part on the winning contention to access the radio frequencyspectrum band.

In some examples, the alignment signal transmission module 2255 may bean example of one or more aspects of the alignment signal transmissionmodule 2040 described with reference to FIG. 20. In some examples, thealignment signal transmission module 2255 may be used to transmit afirst signal, after the apparatus 2205 wins contention to access theradio frequency spectrum band, to indicate a timing of a radio frameboundary associated with the radio frequency spectrum band. In someexamples, the alignment signal transmission module 2255 may transmit thefirst signal while the apparatus 2205 is operating in an LBT-LBE mode ofoperation over the radio frequency spectrum band.

In some examples, the location information transmission module 2260 maybe used to transmit a second signal to convey location information ofoverhead signals in relation to the timing of the radio frame boundary.In some examples, the second signal may include RRC signaling. In someexamples, the second signal may convey location information for adownlink control channel in relation to the radio frame boundary. Insome examples, the second signal may convey location information forresources used for CSI feedback.

In some examples of the apparatus 2205, the first signal transmitted bythe alignment signal transmission module 2255 may include the secondsignal transmitted by the location information transmission module 2260(e.g., the first signal may be a CUBS that conveys the locationinformation for overhead signals in relation to the timing of the radioframe boundary).

FIG. 23 shows a block diagram 2300 of an apparatus 2305 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 2305 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 described with reference to FIG. 17. Theapparatus 2305 may also be a processor. The apparatus 2305 may include areceiver module 2310, a wireless communication management module 2320,and/or a transmitter module 2330. Each of these components may be incommunication with each other.

The components of the apparatus 2305 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2310 may be an example of one ormore aspects of the receiver module 1710 described with reference toFIG. 17. In some examples, the receiver module 2310 may include at leastone radio frequency (RF) receiver, such as at least one RF receiveroperable to receive transmissions over a licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 2310 may be used toreceive various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 2330 may be an example of oneor more aspects of the transmitter module 1730 described with referenceto FIG. 17. In some examples, the transmitter module 2330 may include atleast one RF transmitter, such as at least one RF transmitter operableto transmit over the licensed radio frequency spectrum band and/or theunlicensed radio frequency spectrum band. The transmitter module 2330may be used to transmit various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 2320 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 described with reference to FIG. 17. The wirelesscommunication management module 2320 may include a contention managementmodule 2335 and/or a signal transmission module 2340. Each of thesecomponents may be in communication with each other.

In some examples, the contention management module 2335 may be used toperform a contention procedure to contend for access to one or morechannels of the radio frequency spectrum band for a period of time(e.g., for a frame period of the radio frequency spectrum band). In someexamples, the contention management module 2335 may win contention toaccess the radio frequency spectrum band for a first frame period, whichfirst frame period may be selected from a plurality of different frameperiods (e.g., from a plurality of different frame periods havingdurations of two milliseconds, five milliseconds, and/or tenmilliseconds). In some examples, the first frame period may be an LBTradio frame period. In some examples, each of the plurality of differentframe periods may be an LBT radio frame period.

In some examples, the signal transmission module 2340 may be used totransmit a signal at a periodicity during one or more subframes of thefirst frame period for each of the plurality of different frame periods.In some examples, the periodicity may be a fixed periodicity and/or thesignal transmission module 2340 may transmit the signal at a fixed timeand/or a fixed frequency location, as described, for example, withreference to FIG. 16. In some examples, the signal transmission module2340 may transmit the signal in an overhead channel). The overheadchannels may include a CRS, eCRS, CSI-RS, synchronization signal, and/oran SIB broadcast channel.

FIG. 24 shows a block diagram 2400 of an apparatus 2405 for use inwireless communication, in accordance with various aspects of thepresent disclosure. In some examples, the apparatus 2405 may be anexample of aspects of one or more of the base stations 105, 205, and/or205-a described with reference to FIGS. 1 and/or 2, an example ofaspects of one or more of the UEs 115, 215, 215-a, 215-b, and/or 215-cdescribed with reference to FIGS. 1 and/or 2, and/or an example ofaspects of the apparatus 1705 and/or 2305 described with reference toFIGS. 17 and/or 23. The apparatus 2405 may also be a processor. Theapparatus 2405 may include a receiver module 2410, a wirelesscommunication management module 2420, and/or a transmitter module 2430.Each of these components may be in communication with each other.

The components of the apparatus 2405 may, individually or collectively,be implemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2410 may be an example of one ormore aspects of the receiver module 1710 and/or 2310 described withreference to FIGS. 17 and/or 23. In some examples, the receiver module2410 may include at least one RF receiver, such as at least one RFreceiver operable to receive transmissions over licensed radio frequencyspectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to) and/or anunlicensed radio frequency spectrum band (e.g., a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use). In some examples, the licensed radio frequencyspectrum band and/or the unlicensed radio frequency spectrum band may beused for LTE/LTE-A communications, as described, for example, withreference to FIGS. 1 and/or 2. The receiver module 2410 may in somecases include separate receivers for the licensed radio frequencyspectrum band and the unlicensed radio frequency spectrum band. Theseparate receivers may, in some examples, take the form of a licensed RFspectrum band LTE/LTE-A receiver module 2412 for communicating over thelicensed radio frequency spectrum band, and an unlicensed RF spectrumband LTE/LTE-A receiver module 2414 for communicating over theunlicensed radio frequency spectrum band. The receiver module 2410,including the licensed RF spectrum band LTE/LTE-A receiver module 2412and/or the unlicensed RF spectrum band LTE/LTE-A receiver module 2414,may be used to receive various types of data and/or control signals(i.e., transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the transmitter module 2430 may be an example of oneor more aspects of the transmitter module 1730 and/or 2330 describedwith reference to FIGS. 17 and/or 23. In some examples, the transmittermodule 2430 may include at least one RF transmitter, such as at leastone RF transmitter operable to transmit over the licensed radiofrequency spectrum band and/or the unlicensed radio frequency spectrumband. The transmitter module 2430 may in some cases include separatetransmitters for the licensed radio frequency spectrum band and theunlicensed radio frequency spectrum band. The separate transmitters may,in some examples, take the form of a licensed RF spectrum band LTE/LTE-Atransmitter module 2432 for communicating over the licensed radiofrequency spectrum band, and an unlicensed RF spectrum band LTE/LTE-Atransmitter module 2434 for communicating over the unlicensed radiofrequency spectrum band. The transmitter module 2430, including thelicensed RF spectrum band LTE/LTE-A transmitter module 2432 and/or theunlicensed RF spectrum band LTE/LTE-A transmitter module 2434, may beused to transmit various types of data and/or control signals (i.e.,transmissions) over one or more communication links of a wirelesscommunication system, such as one or more communication links of thewireless communication system 100 and/or 200 described with reference toFIGS. 1 and/or 2. The communication links may be established over thelicensed radio frequency spectrum band and/or the unlicensed radiofrequency spectrum band.

In some examples, the wireless communication management module 2420 maybe an example of one or more aspects of the wireless communicationmanagement module 1720 and/or 2320 described with reference to FIGS. 17and/or 23. The wireless communication management module 2420 may includea frame period selection module 2435, a contention management module2440, a signal collision detection module 2445, and/or a signaltransmission module 2450. Each of these components may be incommunication with each other.

In some examples, the frame period selection module 2435 may be used toselect a first frame period from a plurality of different frame periods(e.g., from a plurality of different frame periods having durations oftwo milliseconds, five milliseconds, and/or ten milliseconds). In someexamples, the first frame period may be an LBT radio frame period. Insome examples, each of the plurality of different frame periods may bean LBT radio frame period.

In some examples, the contention management module 2440 may be anexample of one or more aspects of the contention management module 2335described with reference to FIG. 23. In some examples, the contentionmanagement module 2440 may be used to perform a contention procedure tocontend for access to one or more channels of the radio frequencyspectrum band for a period of time (e.g., for the first frame periodselected by the frame period selection module 2435).

In some examples, the signal collision detection module 2445 may be usedto determine whether a signal to be transmitted at a periodicity duringone or more subframes of the first frame period, and for each of theplurality of different frame periods, collides with a timing of acontention procedure performed by the contention management module 2440.

In some examples, the signal transmission module 2450 may be an exampleof one or more aspects of the signal transmission module 2340 describedwith reference to FIG. 23. In some examples, the signal transmissionmodule 2450 may be used to transmit a signal at a periodicity, duringone or more subframes of the first frame period, and for each of theplurality of different frame periods, when the signal collisiondetection module 2445 determines that the signal will not collide with atiming of a contention procedure performed by the contention managementmodule 2440. In some examples, the periodicity at which the signal istransmitted may be a fixed periodicity and/or the signal may betransmitted at a fixed time and/or a fixed frequency location, asdescribed, for example, with reference to FIG. 16. In some examples, thesignal may be transmitted in an overhead channel, and the overheadchannels may include a CRS, eCRS, CSI-RS, synchronization signal, and/oran SIB broadcast channel.

In some examples, the signal transmission module 2450 may be used toprevent transmission of a signal when the signal collision detectionmodule 2445 determines that the signal collides with a timing of acontention procedure performed by the contention management module 2440,as described, for example, with reference to FIG. 16.

FIG. 25 shows a block diagram 2500 of a base station 2505 (e.g., a basestation forming part or all of an eNB) for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the base station 2505 may be an example ofone or more aspects of the base station 105, 205, and/or 205-a describedwith reference to FIGS. 1 and/or 2, and/or one or more aspects of theapparatus 1705, 1805, 1905, 2005, 2105, 2205, 2305, and/or 2405described with reference to FIGS. 17, 18, 19, 20, 21, 22, 23, and/or 24(e.g., when the apparatus 1705, 1805, 1905, 2005, 2105, 2205, 2305,and/or 2405 is configured as a base station). The base station 2505 maybe configured to implement or facilitate at least some of the basestation and/or apparatus features and functions described with referenceto FIGS. 1, 2, 3, 4, 5, 6, 7, 8A, 8B, 9, 10, 11A, 11B, 11C, 12, 13, 14,15, and/or 16.

The base station 2505 may include a base station processor module 2510,a base station memory module 2520, at least one base station transceivermodule (represented by base station transceiver module(s) 2550), atleast one base station antenna (represented by base station antenna(s)2555), and/or a base station wireless communication management module2560. The base station 2505 may also include one or more of a basestation communications module 2530 and/or a network communicationsmodule 2540. Each of these components may be in communication with eachother, directly or indirectly, over one or more buses 2535.

The base station memory module 2520 may include random access memory(RAM) and/or read-only memory (ROM). The base station memory module 2520may store computer-readable, computer-executable code 2525 containinginstructions that are configured to, when executed, cause the basestation processor module 2510 to perform various functions describedherein related to wireless communication. Alternatively, the code 2525may not be directly executable by the base station processor module 2510but be configured to cause the base station 2505 (e.g., when compiledand executed) to perform various of the functions described herein.

The base station processor module 2510 may include an intelligenthardware device, e.g., a central processing unit (CPU), amicrocontroller, an ASIC, etc. The base station processor module 2510may process information received through the base station transceivermodule(s) 2550, the base station communications module 2530, and/or thenetwork communications module 2540. The base station processor module2510 may also process information to be sent to the transceivermodule(s) 2550 for transmission through the antenna(s) 2555, to the basestation communications module 2530, for transmission to one or moreother base stations 2505-a and 2505-b, and/or to the networkcommunications module 2540 for transmission to a core network 2545,which may be an example of one or more aspects of the core network 130described with reference to FIG. 1. The base station processor module2510 may handle, alone or in connection with the base station wirelesscommunication management module 2560, various aspects of communicatingover (or managing communications over) a first radio frequency spectrumband (e.g., a radio frequency spectrum band for which apparatuses maycontend for access because the radio frequency spectrum band is licensedto multiple users to share access to, such as a licensed radio frequencyspectrum band usable for LTE/LTE-A communications) and/or a second radiofrequency spectrum band (e.g., a radio frequency spectrum band, such asWi-Fi radio frequency spectrum band, for which apparatuses may need tocontend for access because the radio frequency spectrum band isavailable for unlicensed use, such as an unlicensed radio frequencyspectrum band usable for LTE/LTE-A communications).

The base station transceiver module(s) 2550 may include a modemconfigured to modulate packets and provide the modulated packets to thebase station antenna(s) 2555 for transmission, and to demodulate packetsreceived from the base station antenna(s) 2555. The base stationtransceiver module(s) 2550 may, in some examples, be implemented as oneor more base station transmitter modules and one or more separate basestation receiver modules. The base station transceiver module(s) 2550may support communications in the first radio frequency spectrum bandand/or the second radio frequency spectrum band. The base stationtransceiver module(s) 2550 may be configured to communicatebi-directionally, via the antenna(s) 2555, with one or more mobilestations or apparatuses, such as one or more of the UEs 115, 215, 215-a,215-b, and/or 215-c described with reference to FIGS. 1 and/or 2. Thebase station 2505 may, for example, include multiple base stationantennas 2555 (e.g., an antenna array). The base station 2505 maycommunicate with the core network 2545 through the networkcommunications module 2540. The base station 2505 may also communicatewith other base stations, such as the base stations 2505-a and 2505-b,using the base station communications module 2530.

The base station wireless communication management module 2560 may beconfigured to perform and/or control some or all of the features and/orfunctions described with reference to FIGS. 1, 2, 3, 4, 5, 6, 7, 8A, 8B,9, 10, 11A, 11B, 11C, 12, 13, 14, 15, and/or 16 related to wirelesscommunication over the first radio frequency spectrum band and/or thesecond radio frequency spectrum band. For example, the base stationwireless communication management module 2560 may be configured tosupport a supplemental downlink mode, carrier aggregation mode, and/orstandalone mode using the first radio frequency spectrum band and/or thesecond radio frequency spectrum band. The base station wirelesscommunication management module 2560 may include a base stationLTE/LTE-A licensed RF spectrum band module 2565 configured to handleLTE/LTE-A communications in the first radio frequency spectrum band, anda base station LTE/LTE-A unlicensed RF spectrum band module 2570configured to handle LTE/LTE-A communications in the second radiofrequency spectrum band. The base station wireless communicationmanagement module 2560, or portions of it, may include a processor,and/or some or all of the functions of the base station wirelesscommunication management module 2560 may be performed by the basestation processor module 2510 and/or in connection with the base stationprocessor module 2510. In some examples, the base station wirelesscommunication management module 2560 may be an example of the wirelesscommunication management module 1720, 1820, 1920, 2020, 2120, 2220,2320, and/or 2420 described with reference to FIGS. 17, 18, 19, 20, 21,22, 23, and/or 24.

FIG. 26 shows a block diagram 2600 of a UE 2615 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. The UE 2615 may have various configurations and may beincluded or be part of a personal computer (e.g., a laptop computer, anetbook computer, a tablet computer, etc.), a cellular telephone, a PDA,a digital video recorder (DVR), an internet appliance, a gaming console,an e-reader, etc. The UE 2615 may, in some examples, have an internalpower supply (not shown), such as a small battery, to facilitate mobileoperation. In some examples, the UE 2615 may be an example of one ormore aspects of the UE 115, 215, 215-a, 215-b, and/or 215-c describedwith reference to FIGS. 1 and/or 2, and/or one or more aspects of theapparatus 1705, 1805, 1905, 2005, 2105, 2205, 2305, and/or 2405described with reference to FIGS. 17, 18, 19, 20, 21, 22, 23, 24, and/or25 (e.g., when the apparatus 1705, 1805, 1905, 2005, 2105, 2205, 2305,and/or 2405 is configured as a UE). The UE 2615 may be configured toimplement at least some of the UE and/or apparatus features andfunctions described with reference to FIGS. 1, 2, 3, 4, 5, 6, 7, 8A, 8B,9, 10, 11A, 11B, 11C, 12, 13, 14, 15, and/or 16.

The UE 2615 may include a UE processor module 2610, a UE memory module2620, at least one UE transceiver module (represented by UE transceivermodule(s) 2630), at least one UE antenna (represented by UE antenna(s)2640), and/or a UE wireless communication management module 2660. Eachof these components may be in communication with each other, directly orindirectly, over one or more buses 2635.

The UE memory module 2620 may include RAM and/or ROM. The UE memorymodule 2620 may store computer-readable, computer-executable code 2625containing instructions that are configured to, when executed, cause theUE processor module 2610 to perform various functions described hereinrelated to wireless communication. Alternatively, the code 2625 may notbe directly executable by the UE processor module 2610 but be configuredto cause the UE 2615 (e.g., when compiled and executed) to performvarious of the functions described herein.

The UE processor module 2610 may include an intelligent hardware device,e.g., a CPU, a microcontroller, an ASIC, etc. The UE processor module2610 may process information received through the UE transceivermodule(s) 2630 and/or information to be sent to the UE transceivermodule(s) 2630 for transmission through the UE antenna(s) 2640. The UEprocessor module 2610 may handle, alone or in connection with the UEwireless communication management module 2660, various aspects ofcommunicating over (or managing communications over) a first radiofrequency spectrum band (e.g., a radio frequency spectrum band for whichapparatuses may contend for access because the radio frequency spectrumband is licensed to multiple users to share access to, such as alicensed radio frequency spectrum band usable for LTE/LTE-Acommunications) and/or a second radio frequency spectrum band (e.g., aradio frequency spectrum band, such as Wi-Fi radio frequency spectrumband, for which apparatuses may need to contend for access because theradio frequency spectrum band is available for unlicensed use, such asan unlicensed radio frequency spectrum band usable for LTE/LTE-Acommunications).

The UE transceiver module(s) 2630 may include a modem configured tomodulate packets and provide the modulated packets to the UE antenna(s)2640 for transmission, and to demodulate packets received from the UEantenna(s) 2640. The UE transceiver module(s) 2630 may, in someexamples, be implemented as one or more UE transmitter modules and oneor more separate UE receiver modules. The UE transceiver module(s) 2630may support communications in the first radio frequency spectrum bandand/or the second radio frequency spectrum band. The UE transceivermodule(s) 2630 may be configured to communicate bi-directionally, viathe UE antenna(s) 2640, with one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,and/or the apparatus 1705, 1805, 1905, 2005, 2105, 2205, 2305, and/or2405 described with reference to FIGS. 17, 18, 19, 20, 21, 22, 23,and/or 24. While the UE 2615 may include a single UE antenna, there maybe examples in which the UE 2615 may include multiple UE antennas 2640.

The UE state module 2650 may be used, for example, to manage transitionsof the UE 2615 between an RRC idle state and an RRC connected state, andmay be in communication with other components of the UE 2615, directlyor indirectly, over the one or more buses 2635. The UE state module2650, or portions of it, may include a processor, and/or some or all ofthe functions of the UE state module 2650 may be performed by the UEprocessor module 2610 and/or in connection with the UE processor module2610.

The UE wireless communication management module 2660 may be configuredto perform and/or control some or all of the features and/or functionsdescribed with reference to FIGS. 1, 2, 3, 4, 5, 6, 7, 8A, 8B, 9, 10,11A, 11B, 11C, 12, 13, 14, 15, and/or 16 related to wirelesscommunication over the first radio frequency spectrum band and/or thesecond radio frequency spectrum band. For example, the UE wirelesscommunication management module 2660 may be configured to support asupplemental downlink mode, carrier aggregation mode, and/or standalonemode using the first radio frequency spectrum band and/or the secondradio frequency spectrum band. The UE wireless communication managementmodule 2660 may include a UE LTE/LTE-A licensed RF spectrum band module2665 configured to handle LTE/LTE-A communications in the first radiofrequency spectrum band, and a UE LTE/LTE-A unlicensed RF spectrum bandmodule 2670 configured to handle LTE/LTE-A communications in the secondradio frequency spectrum. The UE wireless communication managementmodule 2660, or portions of it, may include a processor, and/or some orall of the functions of the UE wireless communication management module2660 may be performed by the UE processor module 2610 and/or inconnection with the UE processor module 2610. In some examples, the UEwireless communication management module 2660 may be an example of thewireless communication management module 1720, 1820, 1920, 2020, 2120,2220, 2320, and/or 2420 described with reference to FIGS. 17, 18, 19,20, 21, 22, 23, and/or 24.

FIG. 27 is a flow chart illustrating an example of a method 2700 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 2700 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 1805, and/or 1905 described withreference to FIGS. 17, 18, and/or 19. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 2705, the method 2700 may include transmitting a first signalto indicate accessing (e.g., a reserving of) a first channel in a radiofrequency spectrum band. The radio frequency spectrum band may be aradio frequency spectrum band for which apparatuses may need to contendfor access because the radio frequency spectrum band is available forunlicensed use, such as Wi-Fi use. The radio frequency spectrum band mayalso be a shared licensed radio frequency spectrum band which aplurality of mobile network operators are authorized to access. Theoperation(s) at block 2705 may be performed using the wirelesscommunication management module 1720, 1820, 1920, 2560, and/or 2660described with reference to FIGS. 17, 18, 19, 25, and/or 26, and/or thechannel access indication module 1835 and/or 1940 described withreference to FIGS. 18 and/or 19.

In some examples, the first signal may be transmitted using a pluralityof interleaved resource blocks. Transmitting the first signal in thismanner may enable the first signal to occupy at least a certainpercentage of the available frequency bandwidth in the radio frequencyspectrum band and/or satisfy one or more regulatory requirements (e.g.,a requirement that the first signal occupy at least 80% of the availablefrequency bandwidth).

At block 2710, the method 2700 may include transmitting information withthe first signal in the radio frequency spectrum band. The operation(s)at block 2710 may be performed using the wireless communicationmanagement module 1720, 1820, 1920, 2560, and/or 2660 described withreference to FIGS. 17, 18, 19, 25, and/or 26, and/or the informationtransmission module 1840 and/or 1945 described with reference to FIGS.18 and/or 19.

The transmitted information may include various types of information. Insome examples, the information may include a cell ID, a PLMN ID, or acombination thereof. In some examples, the information may indicate aframe structure for transmission in the radio frequency spectrum band(e.g., the LBT radio frame duration). In some examples, the informationmay indicate a number of subframes and/or symbols that will be used fortransmission in a frame structure in the radio frequency spectrum band(e.g., five subframes are used for transmission in a ten millisecondframe duration that includes ten subframes). An indication of a numberof subframes and/or symbols that will be used for transmission in aframe structure in the radio frequency spectrum band may enable areceiving apparatus, such as a UE, to enter a low power state at anearlier time (e.g., immediately after receiving the transmittedsubframes), thereby conserving power. In some examples, the informationmay indicate an uplink configuration and/or a downlink configuration fortransmission in the radio frequency spectrum band (e.g., an uplinkconfiguration and/or a downlink configuration of a frame structure inthe radio frequency spectrum band). An indication of an uplinkconfiguration and/or a downlink configuration for transmission in theradio frequency spectrum band may improve the performance of eIMTAfunctionality. In some examples, the information may indicate whether amaximum number of subframes, of a frame, are used for transmission inthe radio frequency spectrum band (e.g., a single bit may be used toindicate whether a maximum number of subframes are used for transmissionin a frame structure of the radio frequency spectrum band, or whetherfewer than the maximum number of subframes are used for transmission inthe frame structure of the radio frequency spectrum band). In someexamples, the information may indicate a number of antennas to use forreceiving a transmission carried on a component carrier in the radiofrequency spectrum band (e.g., a number of antennas to receivetransmission of the component carrier during a frame structure of theradio frequency spectrum band, as described, for example, with referenceto FIGS. 9 and/or 10). The information may also or alternatively includeany combination of the above types of information and/or other types ofinformation, including other types of system information.

In some examples of the method 2700, the transmitting information withthe first signal may include transmitting information as part of thefirst signal. In these examples, the first signal may be generated basedat least in part on a sequence. The sequence may be a function of theinformation. For example, the sequence may be a function of a cell ID, aPLMN ID, or a combination thereof. The sequence may also oralternatively be a function of any one or combination of the types ofinformation referenced herein.

In other examples in which the transmitting information with the firstsignal may include transmitting information as part of the first signal,the method 2700 may include selecting a first phase from among aplurality of phases for transmission of the first signal. Differentphases of the plurality of phases may correspond to differentinformation. In these examples, the transmitting information with thefirst signal may include transmitting the first signal at the firstphase.

In some examples of the method 2700, the transmitting information withthe first signal may include transmitting information in a second signalalong with the first signal. The second signal may be separate from thefirst signal.

In some examples of the method 2700, the first signal and theinformation may be transmitted during a single OFDM symbol period of theradio frequency spectrum band. In some examples of the method 2700, thefirst signal may be transmitted during a first OFDM symbol period of theradio frequency spectrum band and a second OFDM symbol period of theradio frequency spectrum band, and the information may be transmittedduring the second OFDM symbol period of the radio frequency spectrumband. In some examples, the first OFDM symbol period of the radiofrequency spectrum band and the second OFDM symbol period of the radiofrequency spectrum band may be adjacent OFDM symbol periods.

Thus, the method 2700 may provide for wireless communication. It shouldbe noted that the method 2700 is just one implementation and that theoperations of the method 2700 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 28 is a flow chart illustrating an example of a method 2800 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 2800 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 1805, and/or 1905 described withreference to FIGS. 17, 18, and/or 19. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 2805, the method 2800 may include transmitting a first signalto indicate accessing (e.g., a reserving of) a first channel in a radiofrequency spectrum band. The first signal may be transmitted during afirst OFDM symbol period of the radio frequency spectrum band and asecond OFDM symbol period of the radio frequency spectrum band. In someexamples, the first OFDM symbol period of the radio frequency spectrumband and the second OFDM symbol period of the radio frequency spectrumband may be adjacent OFDM symbol periods. The radio frequency spectrumband may be a radio frequency spectrum band for which apparatuses mayneed to contend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use. The radio frequencyspectrum band may also be a shared licensed radio frequency spectrumband which a plurality of mobile network operators are authorized toaccess. The operation(s) at block 2805 may be performed using thewireless communication management module 1720, 1820, 1920, 2560, and/or2660 described with reference to FIGS. 17, 18, 19, 25, and/or 26, and/orthe channel access indication module 1835 and/or 1940 described withreference to FIGS. 18 and/or 19.

At block 2810, the method 2800 may include transmitting information withthe first signal in the radio frequency spectrum band. The transmittinginformation with the first signal may include transmitting a secondsignal carrying the information. The second signal may be transmittedduring the second OFDM symbol period of the radio frequency spectrumband. The first signal may provide AGC information and/or a phasereference for the second signal. The operation(s) at block 2810 may beperformed using the wireless communication management module 1720, 1820,1920, 2560, and/or 2660 described with reference to FIGS. 17, 18, 19,25, and/or 26, and/or the information transmission module 1840 and/or1945 described with reference to FIGS. 18 and/or 19.

The transmitted information may include various types of information. Insome examples, the information may include a cell ID, a PLMN ID, or acombination thereof. In some examples, the information may indicate aframe structure for transmission in the radio frequency spectrum band(e.g., the LBT radio frame duration). In some examples, the informationmay indicate a number of subframes and/or symbols that will be used fortransmission in a frame structure in the radio frequency spectrum band(e.g., five subframes are used for transmission in a ten millisecondframe duration that includes ten subframes). An indication of a numberof subframes and/or symbols that will be used for transmission in aframe structure in the radio frequency spectrum band may enable areceiving apparatus, such as a UE, to enter a low power state at anearlier time (e.g., immediately after receiving the transmittedsubframes), thereby conserving power. In some examples, the informationmay indicate an uplink configuration and/or a downlink configuration fortransmission in the radio frequency spectrum band (e.g., an uplinkconfiguration and/or a downlink configuration of a frame structure inthe radio frequency spectrum band). An indication of an uplinkconfiguration and/or a downlink configuration for transmission in theradio frequency spectrum band may improve the performance of eIMTAfunctionality. In some examples, the information may indicate whether amaximum number of subframes, of a frame, are used for transmission inthe radio frequency spectrum band (e.g., a single bit may be used toindicate whether a maximum number of subframes are used for transmissionin a frame structure of the radio frequency spectrum band, or whetherfewer than the maximum number of subframes are used for transmission inthe frame structure of the radio frequency spectrum band). In someexamples, the information may indicate a number of antennas to use forreceiving a transmission carried on a component carrier in the radiofrequency spectrum band (e.g., a number of antennas to receivetransmission of the component carrier during a frame structure of theradio frequency spectrum band, as described, for example, with referenceto FIGS. 9 and/or 10). The information may also or alternatively includeany combination of the above types of information and/or other types ofinformation, including other types of system information.

In some examples of the method 2800, the first signal may be transmittedusing a first plurality of interleaved resource blocks and/or the secondsignal may be transmitted using a second plurality of interleavedresource blocks. Transmitting the first signal and/or the second signalin this manner may enable the first signal and/or the second signal tooccupy at least a certain percentage of the available frequencybandwidth in the radio frequency spectrum band and satisfy one or moreregulatory requirements (e.g., a requirement that the first signaloccupy at least 80% of the available frequency bandwidth).

Thus, the method 2800 may provide for wireless communication. It shouldbe noted that the method 2800 is just one implementation and that theoperations of the method 2800 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 29 is a flow chart illustrating an example of a method 2900 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 2900 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 1805, and/or 1905 described withreference to FIGS. 17, 18, and/or 19. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 2905, the method 2900 may include determining a number ofantennas to use for receiving a transmission carried on a componentcarrier in a radio frequency spectrum band. The radio frequency spectrumband may be a radio frequency spectrum band for which apparatuses mayneed to contend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use. The radio frequencyspectrum band may also be a licensed radio frequency spectrum band whicha plurality of mobile network operators are authorized to access. Theoperation(s) at block 2905 may be performed using the wirelesscommunication management module 1720, 1820, 1920, 2560, and/or 2660described with reference to FIGS. 17, 18, 19, 25, and/or 26, and/or theantenna selection module 1960 described with reference to FIG. 19.

In some examples of the method 2900, the determining the number ofantennas to use for receiving a transmission carried on the componentcarrier in the radio frequency spectrum band may include determining thenumber of antennas to use based at least in part on an uplinkconfiguration or a downlink configuration associated with the componentcarrier (e.g., an uplink configuration or a downlink configurationassociated with a frame and/or a subframe of the component carrier). Inthe same or other examples of the method 2900, the determining thenumber of antennas to use for receiving a transmission carried on thecomponent carrier in the radio frequency spectrum band may includedetermining the number of antennas to use based at least in part on acontention procedure associated with each of a plurality of componentcarriers used to serve a UE (e.g., based at least in part on a successor failure of the contention procedure performed for each of theplurality of component carriers).

In some examples of the method 2900, the number of antennas to use forreceiving a transmission carried on the component carrier in the radiofrequency spectrum band may be selected for each subframe of a frame ofthe component carrier. In some examples of the method 2900, the numberof antennas to use for receiving a transmission carried on the componentcarrier in the radio frequency spectrum band may be selected for eachframe of the component carrier.

At block 2910, the method 2900 may include transmitting a first signalto indicate accessing (e.g., a reserving of) a first channel in theradio frequency spectrum band. The operation(s) at block 2910 may beperformed using the wireless communication management module 1720, 1820,1920, 2560, and/or 2660 described with reference to FIGS. 17, 18, 19,25, and/or 26, and/or the channel access indication module 1835 and/or1940 described with reference to FIGS. 18 and/or 19.

At block 2915, the method 2900 may include transmitting information withthe first signal in the radio frequency spectrum band. The informationmay indicate a number of antennas to use for receiving a transmissioncarried on a component carrier in the radio frequency spectrum band(e.g., a number of antennas to receive transmission of the componentcarrier during a frame structure of the radio frequency spectrum band,as described, for example, with reference to FIGS. 9 and/or 10). Theoperation(s) at block 2915 may be performed using the wirelesscommunication management module 1720, 1820, 1920, 2560, and/or 2660described with reference to FIGS. 17, 18, 19, 25, and/or 26, and/or theinformation transmission module 1840 and/or 1945 described withreference to FIGS. 18 and/or 19.

In some examples of the method 2900, the transmitted information mayalso include various other types of information. In some examples, theinformation may include a cell ID, a PLMN ID, or a combination thereof.In some examples, the information may indicate a frame structure fortransmission in the radio frequency spectrum band (e.g., the LBT radioframe duration). In some examples, the information may indicate a numberof subframes and/or symbols that will be used for transmission in aframe structure in the radio frequency spectrum band (e.g., fivesubframes are used for transmission in a ten millisecond frame durationthat includes ten subframes). An indication of a number of subframesand/or symbols that will be used for transmission in a frame structurein the radio frequency spectrum band may enable a receiving apparatus,such as a UE, to enter a low power state at an earlier time (e.g.,immediately after receiving the transmitted subframes), therebyconserving power. In some examples, the information may indicate anuplink configuration and/or a downlink configuration for transmission inthe radio frequency spectrum band (e.g., an uplink configuration and/ora downlink configuration of a frame structure in the radio frequencyspectrum band). An indication of an uplink configuration and/or adownlink configuration for transmission in an unlicensed radio frequencyspectrum band may improve the performance of eIMTA functionality. Insome examples, the information may indicate whether a maximum number ofsubframes, of a frame, are used for transmission in the radio frequencyspectrum band (e.g., a single bit may be used to indicate whether amaximum number of subframes are used for transmission in a framestructure of the radio frequency spectrum band, or whether fewer thanthe maximum number of subframes are used for transmission in the framestructure of the radio frequency spectrum band). The information mayalso or alternatively include any combination of the above types ofinformation and/or other types of information, including other types ofsystem information.

In some examples of the method 2900, the transmitting information withthe first signal may include transmitting information as part of thefirst signal. In these examples, the first signal may be generated basedat least in part on a sequence. The sequence may be a function of theinformation. For example, the sequence may be a function of a cell ID, aPLMN ID, or a combination thereof. The sequence may also oralternatively be a function of any one or combination of the types ofinformation referenced herein.

In some examples of the method 2900, the transmitting information withthe first signal may include transmitting information in a second signalalong with the first signal. The second signal may be separate from thefirst signal.

In some examples, the method 2900 may include selecting a first phasefrom among a plurality of phases for transmission of the first signal.Different phases of the plurality of phases may correspond to differentinformation. In these examples, the transmitting information with thefirst signal may include transmitting the first signal at the firstphase.

In some examples of the method 2900, the first signal and theinformation may be transmitted during a single OFDM symbol period. Insome examples of the method 2900, the first signal may be transmittedduring a first OFDM symbol period and a second OFDM symbol period, andthe information may be transmitted during the second OFDM symbol period.In some examples, the first OFDM symbol period and the second OFDMsymbol period may be adjacent OFDM symbol periods.

In some examples of the method 2900, the first signal may be transmittedusing a plurality of interleaved resource blocks. Transmitting the firstsignal in this manner may enable the first signal to occupy at least acertain percentage of the available frequency bandwidth in the radiofrequency spectrum band and/or satisfy one or more regulatoryrequirements (e.g., a requirement that the first signal occupy at least80% of the available frequency bandwidth).

At block 2920, the method 2900 may include adjusting a precoding matrix,rank, and/or MCS for a data transmission over the component carrier inthe radio frequency spectrum band. The precoding matrix, rank, and/orMCS may be adjusted based at least in part on the number of antennas touse to receive the component carrier in the radio frequency spectrumband, as determined at block 2905. The operation(s) at block 2920 may beperformed using the wireless communication management module 1720, 1820,1920, 2560, and/or 2660 described with reference to FIGS. 17, 18, 19,25, and/or 26, and/or the MCS adjustment module 1965 described withreference to FIG. 19.

At block 2925, the method 2900 may include transmitting the datatransmission over the component carrier in the radio frequency spectrumband, in accordance with the adjusted precoding matrix, rank, and/orMCS. The operation(s) at block 2925 may be performed using the wirelesscommunication management module 1720, 1820, 1920, 2560, and/or 2660described with reference to FIGS. 17, 18, 19, 25, and/or 26, and/or thedata transmission module 1970 described with reference to FIG. 19.

Thus, the method 2900 may provide for wireless communication. It shouldbe noted that the method 2900 is just one implementation and that theoperations of the method 2900 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 30 is a flow chart illustrating an example of a method 3000 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3000 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 2005, 2105, and/or 2205described with reference to FIGS. 17, 20, 21, and/or 22. In someexamples, a base station, UE, and/or apparatus may execute one or moresets of codes to control the functional elements of the base station,UE, and/or apparatus to perform the functions described below.

At block 3005, the method 3000 may include winning contention to accessa radio frequency spectrum band. The radio frequency spectrum band maybe a radio frequency spectrum band for which apparatuses may need tocontend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use. The radio frequencyspectrum band may also be a licensed radio frequency spectrum band whicha plurality of mobile network operators are authorized to access. Theoperation(s) at block 3005 may be performed using the wirelesscommunication management module 1720, 2020, 2120, 2220, 2560, and/or2660 described with reference to FIGS. 17, 20, 21, 22, 25, and/or 26,and/or the contention management module 2035, 2140, and/or 2235described with reference to FIGS. 20, 21, and/or 22.

After the winning contention to access the radio frequency spectrumband, and at block 3010, the method 3000 may include transmitting afirst signal to align a starting point of a second signal with areference boundary associated with the radio frequency spectrum band. Insome examples, the first signal may be transmitted before the secondsignal. The operation(s) at block 3010 may be performed using thewireless communication management module 1720, 2020, 2120, 2220, 2560,and/or 2660 described with reference to FIGS. 17, 20, 21, 22, 25, and/or26, and/or the alignment signal transmission module 2040, 2150, and/or2255 described with reference to FIGS. 20, 21, and/or 22.

In some examples of the method 3000, the first signal may include avariable length training sequence. The variable length training sequencemay, in some examples, include one or more transmission units of fixedduration. In other examples of the method 3000, the first signal mayinclude a variable length training sequence and at least one fixedlength training sequence.

In some examples of the method 3000, the second signal may include asignal indicating the winning contention to access the radio frequencyspectrum band (e.g., a CUBS). In other examples of the method 3000(e.g., examples in which a transmitting apparatus is operating in anLBT-LBE mode of operation in the radio frequency spectrum band), thesecond signal may include a data transmission.

In examples of the method 3000, the reference boundary may include aboundary of an OFDM symbol period. In these examples, a contentionprocedure may be performed in accordance with a contention priorityduring the OFDM symbol period. The contention priority may determinewhen an apparatus (e.g., a base station or UE performing the method3000) performs a contention procedure within the OFDM symbol periodassociated with the radio frequency spectrum band. Thus, the contentionpriority may provide, to an apparatus that performs a contentionprocedure earlier in time, a preference for winning the contentionprocedure over an apparatus that performs a contention procedure laterin time. In some examples of the method 3000, the first signal may beassociated with the contention priority of its transmitting apparatus(e.g., a base station or UE performing the method 3000), such that thefirst signal is transmitted during a portion of the OFDM symbol periodbased at least in part on the contention priority. Thus, for example,the first signal may be transmitted over a greater portion of the OFDMsymbol period when the first signal is associated with a contentionpriority that allows an apparatus to perform a contention procedureearlier within the OFDM symbol period. Similarly, and by way of furtherexample, the first signal may be transmitted over a smaller portion ofthe OFDM symbol period when the first signal is associated with acontention priority that allows an apparatus to perform a contentionprocedure later within the OFDM symbol period.

In some examples, the reference boundary may include a boundary of aslot of a frame associated with the radio frequency spectrum band and/ora boundary of a subframe of a frame associated with the radio frequencyspectrum band.

In some examples, the method 3000 may include transmitting informationas part of the first signal. The information may include, for example,AGC information and/or a phase reference for the second signal.

In some examples of the method 3000, the first signal and/or the secondsignal may be transmitted using a plurality of interleaved resourceblocks. Transmitting the first signal and/or the second signal in thismanner may enable the first signal and/or the second signal to occupy atleast a certain percentage of the available frequency bandwidth in theradio frequency spectrum band and/or satisfy one or more regulatoryrequirements (e.g., a requirement that the first signal and/or secondsignal occupy at least 80% of the available frequency bandwidth).

Thus, the method 3000 may provide for wireless communication. It shouldbe noted that the method 3000 is just one implementation and that theoperations of the method 3000 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 31 is a flow chart illustrating an example of a method 3100 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3100 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 2005, and/or 2105 described withreference to FIGS. 17, 20, and/or 21. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 3105, the method 3100 may include accessing timing information.The timing information may include, for example, a timing of one or morereference boundaries associated with a radio frequency spectrum band.The radio frequency spectrum band may be a radio frequency spectrum bandfor which apparatuses may need to contend for access because the radiofrequency spectrum band is available for unlicensed use, such as Wi-Fiuse. The radio frequency spectrum band may also be a licensed radiofrequency spectrum band which a plurality of mobile network operatorsare authorized to access. The operation(s) at block 3105 may beperformed using the wireless communication management module 1720, 2020,2120, 2560, and/or 2660 described with reference to FIGS. 17, 20, 21,25, and/or 26, and/or the timing information access module 2135described with reference to FIG. 21.

At block 3110, the method 3100 may include winning contention to accessa radio frequency spectrum band. The radio frequency spectrum band maybe a radio frequency spectrum band for which apparatuses may need tocontend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use. The radio frequencyspectrum band may also be a licensed radio frequency spectrum band whicha plurality of mobile network operators are authorized to access. Theoperation(s) at block 3110 may be performed using the wirelesscommunication management module 1720, 2020, 2120, 2560, and/or 2660described with reference to FIGS. 17, 20, 21, 25, and/or 26, and/or thecontention management module 2035 and/or 2140 described with referenceto FIGS. 20 and/or 21.

At block 3115, the method 3100 may include determining a referenceboundary (e.g., a reference boundary occurring after the winningcontention to access the radio frequency spectrum band) associated withthe radio frequency spectrum band, based at least in part on the timinginformation and the winning contention to access the radio frequencyspectrum band. The operation(s) at block 3115 may be performed using thewireless communication management module 1720, 2020, 2120, 2560, and/or2660 described with reference to FIGS. 17, 20, 21, 25, and/or 26, and/orthe reference boundary determination module 2145 described withreference to FIG. 21.

After the winning contention to access the radio frequency spectrumband, and at block 3120, the method 3100 may include transmitting afirst signal to align a starting point of a second signal with thedetermined reference boundary associated with the radio frequencyspectrum band. In some examples, the first signal may be transmittedbefore the second signal. The operation(s) at block 3120 may beperformed using the wireless communication management module 1720, 2020,2120, 2560, and/or 2660 described with reference to FIGS. 17, 20, 21,25, and/or 26, and/or the alignment signal transmission module 2040and/or 2150 described with reference to FIGS. 20 and/or 21.

In some examples of the method 3100, the first signal may include avariable length training sequence. The variable length training sequencemay, in some examples, include one or more transmission units of fixedduration. In other examples of the method 3000, the first signal mayinclude a variable length training sequence and at least one fixedlength training sequence.

In some examples of the method 3100, the second signal may include asignal indicating the winning contention to access the radio frequencyspectrum band (e.g., a CUBS). In other examples of the method 3000(e.g., examples in which a transmitting apparatus is operating in anLBT-LBE mode of operation in the radio frequency spectrum band), thesecond signal may include a data transmission.

In examples of the method 3100, the reference boundary may include aboundary of an OFDM symbol period. In these examples, a contentionprocedure may be performed in accordance with a contention priorityduring the OFDM symbol period. The contention priority may determinewhen an apparatus (e.g., a base station or UE performing the method3100) performs a contention procedure within the OFDM symbol periodassociated with the radio frequency spectrum band. Thus, the contentionpriority may provide, to an apparatus that performs the contentionprocedure earlier in time, a preference for winning the contentionprocedure over an apparatus that performs the contention procedure laterin time. In some examples of the method 3100, the first signal may beassociated with the contention priority of its transmitting apparatus(e.g., a base station or UE performing the method 3100), such that thefirst signal is transmitted during a portion of the OFDM symbol periodbased at least in part on the contention priority. Thus, for example,the first signal may be transmitted over a greater portion of the OFDMsymbol period when the first signal is associated with a contentionpriority that allows an apparatus to perform a contention procedureearlier within the OFDM symbol period. Similarly, and by way of furtherexample, the first signal may be transmitted over a smaller portion ofthe OFDM symbol period when the first signal is associated with acontention priority that allows an apparatus to perform a contentionprocedure later within the OFDM symbol period.

In some examples, the reference boundary may include a boundary of aslot of a frame associated with the radio frequency spectrum band and/ora boundary of a subframe of a frame associated with the radio frequencyspectrum band.

In some examples, the method 3100 may include transmitting informationas part of the first signal. The information may include, for example,AGC information and/or a phase reference for the second signal.

In some examples of the method 3100, the first signal and/or the secondsignal may be transmitted using a plurality of interleaved resourceblocks. Transmitting the first signal and/or the second signal in thismanner may enable the first signal and/or the second signal to occupy atleast a certain percentage of the available frequency bandwidth in theradio frequency spectrum band and/or satisfy one or more regulatoryrequirements (e.g., a requirement that the first signal and/or secondsignal occupy at least 80% of the available frequency bandwidth).

Thus, the method 3100 may provide for wireless communication. It shouldbe noted that the method 3100 is just one implementation and that theoperations of the method 3100 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 32 is a flow chart illustrating an example of a method 3200 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3200 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 2005, and/or 2205 described withreference to FIGS. 17, 20, and/or 22. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 3205, the method 3200 may include winning contention to accessa radio frequency spectrum band. The radio frequency spectrum band maybe a radio frequency spectrum band for which apparatuses may need tocontend for access because the radio frequency spectrum band isavailable for unlicensed use, such as Wi-Fi use. The radio frequencyspectrum band may also be a shared licensed radio frequency spectrumband which a plurality of mobile network operators are authorized toaccess. The operation(s) at block 3205 may be performed using thewireless communication management module 1720, 2020, 2220, 2560, and/or2660 described with reference to FIGS. 17, 20, 22, 25, and/or 26, and/orthe contention management module 2035 and/or 2235 described withreference to FIGS. 20 and/or 22. In some examples, the winningcontention to access the radio frequency spectrum band may be achievedwhile operating in an LBT-LBE mode of operation over the radio frequencyspectrum band.

After the winning contention to access the radio frequency spectrumband, and at block 3210, the method 3200 may include transmitting afirst signal to indicate a timing of a radio frame boundary associatedwith the radio frequency spectrum band. The operation(s) at block 3210may be performed using the wireless communication management module1720, 2020, 2220, 2560, and/or 2660 described with reference to FIGS.17, 20, 22, 25, and/or 26, the alignment signal transmission module 2040and/or 2255 described with reference to FIGS. 20 and/or 22, and/or thereference boundary determination module 2250 described with reference toFIG. 22.

At block 3215, the method 3200 may include transmitting a second signalto convey location information for overhead signals in relation to thetiming of the radio frame boundary. In some examples, the second signalmay include RRC signaling. In some examples, the second signal mayconvey location information for a downlink control channel in relationto the radio frame boundary. In some examples, the second signal mayconvey location information for resources used for CSI feedback. Theoperation(s) at block 3215 may be performed using the wirelesscommunication management module 1720, 2020, 2220, 2560, and/or 2660described with reference to FIGS. 17, 20, 22, 25, and/or 26, and/or thelocation information transmission module 2260 described with referenceto FIG. 22.

In some examples of the method 3200, the first signal may include thesecond signal (e.g., the first signal may be a CUBS that conveys thelocation information for overhead signals in relation to the timing ofthe radio frame boundary).

FIG. 33 is a flow chart illustrating an example of a method 3300 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3300 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 2305, and/or 2405 described withreference to FIGS. 17, 23, and/or 24. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 3305, the method 3300 may include winning contention to accessa radio frequency spectrum band during a first frame period. The firstframe period may be selected from a plurality of different frame periods(e.g., from a plurality of different frame periods having durations oftwo milliseconds, five milliseconds, and/or ten milliseconds). In someexamples, the first frame period may be an LBT radio frame period. Insome examples, each of the plurality of different frame periods may bean LBT radio frame period. The radio frequency spectrum band may be aradio frequency spectrum band for which apparatuses may need to contendfor access because the radio frequency spectrum band is available forunlicensed use, such as Wi-Fi use. The radio frequency spectrum band mayalso be a shared licensed radio frequency spectrum band which aplurality of mobile network operators are authorized to access. Theoperation(s) at block 3305 may be performed using the wirelesscommunication management module 1720, 2320, 2420, 2560, and/or 2660described with reference to FIGS. 17, 23, 24, 25, and/or 26, and/or thecontention management module 2335 and/or 2440 described with referenceto FIGS. 23 and/or 24.

At block 3310, the method 3300 may include transmitting a signal at aperiodicity during one or more subframes of the first frame period foreach of the plurality of different frame periods. In some examples, theperiodicity may be a fixed periodicity and/or the signal may betransmitted at a fixed time and/or a fixed frequency location, asdescribed, for example, with reference to FIG. 16. The operation(s) atblock 3310 may be performed using the wireless communication managementmodule 1720, 2320, 2420, 2560, and/or 2660 described with reference toFIGS. 17, 23, 24, 25, and/or 26, and/or the signal transmission module2340 and/or 2450 described with reference to FIGS. 23 and/or 24.

In some examples, the signal may be transmitted in an overhead channel,and the overhead channels may include a CRS, eCRS, CSI-RS,synchronization signal, and/or an SIB broadcast channel.

Thus, the method 3300 may provide for wireless communication. It shouldbe noted that the method 3300 is just one implementation and that theoperations of the method 3300 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 34 is a flow chart illustrating an example of a method 3400 forwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3400 is described below withreference to aspects of one or more of the base stations 105, 205,205-a, and/or 2505 described with reference to FIGS. 1, 2, and/or 25,aspects of one or more of the UEs 115, 215, 215-a, 215-b, 215-c, and/or2615 described with reference to FIGS. 1, 2, and/or 26, and/or aspectsof one or more of the apparatuses 1705, 2305, and/or 2405 described withreference to FIGS. 17, 23, and/or 24. In some examples, a base station,UE, and/or apparatus may execute one or more sets of codes to controlthe functional elements of the base station, UE, and/or apparatus toperform the functions described below.

At block 3405, the method 3400 may include selecting a first frameperiod from a plurality of different frame periods (e.g., from aplurality of different frame periods having durations of twomilliseconds, five milliseconds, and/or ten milliseconds). In someexamples, the first frame period may be an LBT radio frame period. Insome examples, each of the plurality of different frame periods may bean LBT radio frame period. The operation(s) at block 3405 may beperformed using the wireless communication management module 1720, 2320,2420, 2560, and/or 2660 described with reference to FIGS. 17, 23, 24,25, and/or 26, and/or the frame period selection module 2435 describedwith reference to FIG. 24.

At block 3410, the method 3400 may include winning contention to accessa radio frequency spectrum band during the first frame period. Theunlicensed radio frequency spectrum band may be a radio frequencyspectrum band for which apparatuses may need to contend for accessbecause the radio frequency spectrum band is available for unlicenseduse, such as Wi-Fi use. The radio frequency spectrum band may also be ashared licensed radio frequency spectrum band which a plurality ofmobile network operators are authorized to access. The operation(s) atblock 3410 may be performed using the wireless communication managementmodule 1720, 2320, 2420, 2560, and/or 2660 described with reference toFIGS. 17, 23, 24, 25, and/or 26, and/or the contention management module2335 and/or 2440 described with reference to FIGS. 23 and/or 24.

At block 3415, the method 3400 may include determining whether a signalto be transmitted at a periodicity during one or more subframes of thefirst frame period, and for each of the plurality of different frameperiods, collides with a timing of a contention procedure. When it isdetermined that the signal does not collide with the timing of thecontention procedure, block 3420 may direct the flow of the method 3400to block 3425. When it is determined that the signal collides with thetiming of the contention procedure, block 3420 may direct the flow ofthe method 3400 to block 3430. The operation(s) at block 3415 and/orblock 3420 may be performed using the wireless communication managementmodule 1720, 2320, 2420, 2560, and/or 2660 described with reference toFIGS. 17, 23, 24, 25, and/or 26, and/or the signal collision detectionmodule 2445 described with reference to FIG. 24.

At block 3425, the method 3400 may include transmitting a signal at aperiodicity during one or more subframes of the first frame period, andfor each of the plurality of different frame periods. In some examples,the periodicity may be a fixed periodicity and/or the signal may betransmitted at a fixed time and/or a fixed frequency location, asdescribed, for example, with reference to FIG. 16. The operation(s) atblock 3425 may be performed using the wireless communication managementmodule 1720, 2320, 2420, 2560, and/or 2660 described with reference toFIGS. 17, 23, 24, 25, and/or 26, and/or the signal transmission module2340 and/or 2450 described with reference to FIGS. 23 and/or 24.

In some examples, the signal may be transmitted in an overhead channel,and the overhead channels may include a CRS, eCRS, CSI-RS,synchronization signal, and/or an SIB broadcast channel.

At block 3430, the method 3400 may include preventing transmission ofthe signal based at least in part on a determination that the signalcollides with the timing of the contention procedure, as described, forexample, with reference to FIG. 16. The operation(s) at block 3430 maybe performed using the wireless communication management module 1720,2320, 2420, 2560, and/or 2660 described with reference to FIGS. 17, 23,24, 25, and/or 26, and/or the signal transmission module 2340 and/or2450 described with reference to FIGS. 23 and/or 24.

Thus, the method 3400 may provide for wireless communication. It shouldbe noted that the method 3400 is just one implementation and that theoperations of the method 3400 may be rearranged or otherwise modifiedsuch that other implementations are possible.

In some examples, aspects of one or more of the methods 2700, 2800,2900, 3000, 3100, 3200, 3300, and/or 3400 may be combined.

The detailed description set forth above in connection with the appendeddrawings describes examples and does not represent the only examplesthat may be implemented or that are within the scope of the claims. Theterms “example” and “exemplary,” when used in this description, mean“serving as an example, instance, or illustration,” and not “preferred”or “advantageous over other examples.” The detailed description includesspecific details for the purpose of providing an understanding of thedescribed techniques. These techniques, however, may be practicedwithout these specific details. In some instances, well-known structuresand apparatuses are shown in block diagram form in order to avoidobscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on anon-transitory computer-readable medium. Other examples andimplementations are within the scope and spirit of the disclosure andappended claims. For example, due to the nature of software, functionsdescribed above can be implemented using software executed by aprocessor, hardware, firmware, hardwiring, or combinations of any ofthese. Features implementing functions may also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations. Also, as usedherein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of” indicates a disjunctive list such that,for example, a list of “at least one of A, B, or C” means A or B or C orAB or AC or BC or ABC (i.e., A and B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communications, comprising:winning contention during a first symbol period to access a radiofrequency spectrum band; and after the winning contention to access theradio frequency spectrum band, transmitting, during the first symbolperiod, a first signal to align a starting point of a second signal in asecond symbol period with a reference boundary at an ending point of thefirst symbol period, the second symbol period beginning subsequent tothe first symbol period and following the reference boundary, thereference boundary associated with the radio frequency spectrum band,wherein the first signal comprises a variable length sequence.
 2. Themethod of claim 1, wherein the radio frequency spectrum band comprisesan unlicensed radio frequency spectrum band.
 3. The method of claim 1,further comprising: accessing timing information; and determining thereference boundary based at least in part on the timing information andthe winning contention to access the radio frequency spectrum band. 4.The method of claim 1, wherein the variable length sequence comprises avariable length training sequence.
 5. The method of claim 1, wherein thefirst signal further comprises at least one fixed length trainingsequence.
 6. The method of claim 1, further comprising: operating in alisten before talk (LBT)-load based equipment (LBE) mode of operation inthe radio frequency spectrum band.
 7. The method of claim 1, wherein thesecond signal comprises a beacon signal.
 8. The method of claim 1,wherein the reference boundary comprises a boundary of an orthogonalfrequency-division multiplexing (OFDM) symbol period associated with theradio frequency spectrum band.
 9. The method of claim 8, wherein thefirst signal is associated with a contention priority, and wherein thefirst signal is transmitted during a portion of the OFDM symbol periodbased at least in part on the contention priority.
 10. An apparatus forwireless communications, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memory,the instructions being executable by the processor to: win contentionduring a first symbol period to access a radio frequency spectrum band;and after winning contention to access the radio frequency spectrumband, transmit, during the first symbol period, a first signal to aligna starting point of a second signal in a second symbol period with areference boundary at an ending point of the first symbol period, thesecond symbol period beginning subsequent to the first symbol period andfollowing the reference boundary, the reference boundary associated withthe radio frequency spectrum band, wherein the first signal comprises avariable length sequence.
 11. The apparatus of claim 10, wherein thesecond signal comprises a beacon signal.